Proceedings Volume 1145

7th Intl Conf on Fourier Transform Spectroscopy

David G. Cameron
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Proceedings Volume 1145

7th Intl Conf on Fourier Transform Spectroscopy

David G. Cameron
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 1 December 1989
Contents: 1 Sessions, 271 Papers, 0 Presentations
Conference: Seventh International Conference on Fourier and Computerized Infrared Spectroscopy 1989
Volume Number: 1145

Table of Contents

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Table of Contents

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Infrared, Raman, And Normal Mode Studies Of Structure In Peptides And Proteins
Samuel Krimm
Recent advances in normal mode analysis of peptides and proteins have enhanced our ability to interpret IR and Raman spectra of such molecules in terms of their structure. We review the development of an empirical vibrational force field for doing such calculations, show how it can be useful in spectral analysis, band assignments, and structure determination, and indicate how ab initio methods can provide more detailed insights into the nature of such force fields.
Fast Time-Resolved Fourier Transform Spectroscopy With Rapid-Scan Interferometers
J J Sloan
Although it is a relatively new technique, time-resolved Fourier transform Spectroscopy (TRFTS) has already been used in a large number of different fields, including biochemists (1-5) natural products chemistry (6-14) environmental studies( 15-21) combustion and thermochemistry(22-28) electrochemistry(29,30) polymer chemistry(31-36)and gas kinetics(37-40) and dynamics(41 -46). In many of these studies the technique has been combined with other, very powerful, analytical techniques such as attenuated total reflectance (29-31,47)and gas chromatography (48-51)to provide information which is, for the most part, unavailable by other methods.
Langmuir Revisited: Using Infrared Reflectance Spectroscopy To Determine Monolayer Structure At Liquid Interfaces
Richard A. Dluhy
Over the past several years, this laboratory has adapted external reflection-absorption infrared spectroscopy to the study of conformation-sensitive vibrational modes in amphiphilic monolayers at the air-water (NW) interface. It has proven possible to investigate the surface pressure-induced first order thermodynamic phase transition of phospholipid monolayer films at the A/W interface using this technique. The IR results to date indicate that this phase transition is accompanied by a change in conformational order in the hydrocarbon portion of the molecule and suggests that the monolayer is heterogeneous and biphasic in character, with coexistence of molecular domains throughout the phase transition. More recently, we have explored the charged, hydrophilic head group region of the amphiphilic monolayer and the interaction of sub-phase ions and pH with the molecule's interfacial ionic groups. The spectra obtained of the head group region in the monolayer films clearly indicate that the relevant vibrational modes are sensitive to hydration and protonation of the ionic groups in the monolayer. These results strongly suggest that the external reflection technique described here has the requisite sensitivity to probe questions involving complex physical chemistry and interfacial structure in amphiphilic monolayer films at the A/W interface and may be useful in describing the detailed molecular structure of such films.
Case Studies Of Molecular Identification, Structure Determination, And Internal Molecular Dynamics Using High Resolution FT-IR
Brenda P. Winnewisser, Manfred Winnewisser
A variety of problems will be shown which we have been able to approach in the Giessen laboratory using the Bruker IFS 120 HR high resolution interferometer. The species HNCNH has now been fully characterized from its gas phase IR spectrum. Recently we have identified the molecule CNCN, which had not been detected using other analytical and spectroscopic methods. Our high resolution data have yielded the first accurate structure for a well-known species, SCCCS, and direct confirmation of the linear structure of the extended carbon suboxide, OCCCCCO. Further, we have investigated the internal dynamics of SCCCS, OCCCS, OCCCCCO, HSSH, HNCNH and HCNO. The study of the 13C-substituted species of HCNO revealed a novel form of Coriolis resonance.
Structure And Kinetics Of Molecules At Surfaces
Yves J. Chabal
After a brief review of static (i.e. structural) studies of atoms and molecules at surfaces, a time-resolved infrared experiment is presented that measures the diffusion of CO molecules on a platinum surface. The time resolution of this pulsed molecular beam doser/Fourier Transform interferometer system is 5 ms, making it possible to measure molecular hopping rates (diffusion) over 5 orders of magnitude.
Matrix FTIR Spectroscopy Of Transient Species
Lester Andrews
Matrix studies featuring the FTIR instrumental advantages of resolution and sensitivity for a finite amount of time will be described. Ammonia clusters have a complicated spectrum in the N-H stretching region. One antisymmetric and two symmetric stretching modes in the dimer verify an asymmetric cyclic dimer structure.' Chlorine isotopic splittings have been resolved for the four H/D substituted (HC1)3 species, which confirm the cluster stoichiometry and triangular structure.2 The ammonia/hydrogen cyanide system reveals 1:1 and 1:2 complexes, which are identified from their FTIR spectra and characterized by comparison to similar complexes.3 The ozone/hydrogen fluoride system gives the 03--HF complex, and mixed oxygen isotopic spectra show inequivalent terminal oxygen atoms.4 The symmetrical PH3--03 complex photolyses to give an asymmetric HOP02 species based on mixed isotopic spectra.5
High Resolution Fourier Transform Spectroscopy In The Ultra-Violet
Anne Thorne
The reasons for extending Fourier transform spectroscopy from the infra-red and visible regions into the ultra-violet are discussed, and a range of possible applications is given. The principle features of an instrument designed and built to work from the visible region to the spectrosil cut-off at about 175 nm are described, and examples are given of some problems to which this instrument has been applied, including a preliminary investigation of the feasibility of using a pulsed source. Finally, the possibilities of extending the spectral range of FTS further into the ultra-violet are briefly discussed.
Computers And Computing In FT-IR Spectroscopy
Don Kuehl, James Duckworth
The state-of-the-art in inexpensive computing for FT-IR spectroscopy is examined. Problems concerning instrument communications, data transportability, networking using personal computers are explored. The use of personal computers in advanced chemometric applications is examined including applications of discriminant analysis for the classification of chemically similar compounds.
Techniques And Application Of FTIR Vibrational Circular Dichroism
T. A. Keiderling, S. C. Yasui, P. Malon, et al.
Vibrational Circular Dichroism (VCD) has proven to be useful for detecting conformational change and for characterizing secondary structures for a variety of biopolymers. Use of FTIR-based VCD for such problems has been made possible with recent improvements in optical design and S/N. FTIR-VCD and dispersive VCD each have strengths that are optimal for specific problems. A comparison of techniques is presented in this lecture, and selected examples of VCD applications to polypeptides and proteins are given.
A Systems-Analytical Approach To Action Spectroscopy In Biology And Medicine: Fourier Interferometric Stimulation (FIS)
Roland Gemperlein
A systems-analytical method, using the Michelson Interferometer as a spectral light modulator to determine spectral sensitivity in animals and in man, is described. The interferogram of the light source acts as stimulus to the system. Historical development, apparatus and the results of different applications are presented.
Radiometrically Accurate FTS For Atmospheric Emission Observations
H E. Revercomb, W. L. Smith, L. A Sromovsky, et al.
The calibration procedures and radiometric performance of the High-resolution Interferometer Sounder (HIS) aircraft instrument are discussed to illustrate the superior performance of FTIR instrumentation for achieving accurate emission measurements of the atmosphere. Radiometrically accurate emission spectra of the earth have been observed both from the NASA U2/ER2 aircraft and from the ground in the spectral range from 3.8 to 16.6 Am with resolving powers of 1800-3800. While the HIS was primarily designed for atmospheric temperature and moisture profiling, its broad spectral coverage leads to a wide range of important applications. The HIS was designed to give absolute brightness temperature errors of less than 1.0°C and a reproducibility of 0.1°C. Laboratory tests indicate that these goals were achieved over most of the measurement domain. The single scan detector noise is somewhat larger than the reproducibility. Agreement is remarkably good between HIS spectra and calculations from radiosonde temperature and water vapor profiles using the AFGL FASCOD2 program, a tribute to the current state of line-by-line codes. Brightness temperature differences are, less than 1-2°C over much of the spectral domain, with some important exceptions. The largest discrepancies, currently at the CO2 Q-branches, will be greatly reduced when recent improvements in the treatment of line mixing are released in FASCOD3. Other substantial differences have recently been identified as resulting from trace gas absorption, CO2 and H2O line strength uncertainties, and from uncertainties in the strength of the H2O foreign broadened continuum.
Fourier Transform Spectroscopy Of Semiconductor Photoluminescence
R. Brent Young, Nelson L. Rowell
A Fourier transform infrared (FT-IR) spectrometer has been combined with a PL apparatus for the study of semiconductors. Fourier transform spectroscopy has certain advantages for PL, especially in the infrared, including improved signal to noise, higher abscissa precision and resolution. A brief review of the technique is given and we discuss, as examples, the optimization of the FT-IR apparatus for the study of near gap dopant states and deep trap related transitions in epitaxial Si films grown by molecular beam epitaxy (MBE) and double modulation techniques for the study of narrow gap materials, such as InSb. In studying arsenic doped MBE silicon, we found bound-exciton (BE) peaks associated with substitutional As atoms to be the dominant features in the 4.2 K PL spectra from 6 pm thick films grown on n+ (Sb-doped) substrates at growth temperatures ranging from 500 to 800 C. For samples grown at the lower temperatures ~500 C, we observed additional, lower energy, no-phonon peaks due to residual ion-induced lattice defects and a broad, possibly trap related, background rising towards 750 meV (6000 cm-1). These features were not observed in the spectra of samples grown at higher temperatures and this work, which has been cross referenced with other techniques such as deep level transient spectroscopy (DLTS), will lead to optimization of growth conditions for ion-doped n and p type MBE silicon. In the study of materials with narrower gaps such as InSb, a technique using double modulation - interferometer and excitation source - was used to remove the effects of the thermal background radiation. This technique is described and compared with the conventional subtraction procedure. A 77 K InSb detector was used to observe and resolve near gap emission at 5.3 pm and a HgCdTe detector to discover longer wave impurity related emission. The results obtained include the effects of sample temperature 5-20 K and pump laser power density on the individual lines in the spectra.
FTIR Measurements Of Minor Atmospheric Constituents
F. J. Murcray, D. G. Murcray, F. H. Murcray, et al.
The major components of the Earth's atmosphere, nitrogen, oxygen and argon, are essentially transparent to infrared radiation. Most of the minor and trace gases in the atmosphere have significant infrared absorptions, which provide a means of measuring their abundance. For many years, we have been using the infrared as a remote sensing tool. As Fourier Transform systems (FTS) have developed, they have been increasingly used in our work. We primarily use two techniques for atmospheric measurements: solar absorption spectra and atmospheric emission spectra. In the solar absorption case, the sun is used as an intense source, and the measurement is similar (in principle) to that carried out routinely in the laboratory. Unfortunately, no reference (vacuum) path is readily available, the sample (atmosphere) is not under uniform temperature or pressure conditions and the composition is not uniform. Despite the complications, accurate determinations of gas amounts can be made in many cases, and path lengths unattainable in the laboratory can yield significant information about the molecular spectroscopy of some compounds. Interferometer systems have advantages for recording solar spectra in the infrared: relatively small size for comparable resolution and a highly accurate frequency scale. In most cases there is no multiplex advantage, but the throughput may be higher. FTS can also cover broad spectral intervals, which allows quantification of several gases simultaneously. The atmosphere is a very weak infrared source, and instrument sensitivity is of primary importance. FTS may or may not have a multiplex advantage, but it still provides an accurate frequency scale and substantial throughput.
High-Resolution Far-Infrared FT Spectroscopy Of The Stratosphere: Optimization Of The Optical Design Of The Instrument
Bruno Carli
The optical configuration of the mirrors in the two arms of an interferometer determines the length of the movement needed to obtain a required spectral resolution and the alignment tolerances needed to obtain adequate fringe visibility. The configurations that provide an enhancement of the maximum path difference, as well as the the configurations that provide a compensation for the alignment errors, are briefly reviewed. The optical configuration of a space-borne high-resolution far-infrared spectrometer for the study of the earth's stratosphere is presented.
Fourier-Transform Raman Spectroscopy Of Biological Assemblies
Ira W. Levin, E. Neil Lewis
Although the successful coupling of Raman scattered near-infrared radiation to a Michelson interferometer has recently created an outburst of intense interest in Fourier-transform (FT) Raman spectrometry," extended applications of the technique to macromolecular assemblies of biochemical and biophysical relevance have not progressed as rapidly as studies directed primarily at more conventional chemical characterizations. Since biological materials sampled with visible laser excitation sources typically emit a dominant fluorescence signal originating either from the intrinsic fluorescence of the molecular scatterer or from unrelenting contaminants, the use of near-infrared Nd:YAG laser excitation offers a convenient approach for avoiding this frequently overwhelming effect. In addition, the FT-Raman instrumentation provides a means of eliminating the deleterious resonance and decomposition effects often observed with the more accessible green and blue laser emissions. However, in choosing the incident near-infrared wavelength at, for example, 1064nm, the Raman scattered intensity decreases by factors of eighteen to forty from the Raman emissions induced by the shorter, visible excitations. Depending upon the experiment, this disadvantage is offset by the throughput and multiplex advantages afforded by the interferometric design. Thus, for most chemical systems, near-infrared FT-Raman spectroscopy, clearly provides a means for obtaining vibrational Raman spectra from samples intractable to the use of visible laser sources. In particular, for neat liquids, dilute solutions or polycrystalline materials, the ability to achieve high quality, reproducible spectra is, with moderate experience and perhaps relatively high laser powers, as straightforward as the conventional methods used to obtain Raman spectra with visible excitation and dispersive monochromators. In using near-infrared FT techniques to determine the Raman spectra of biological samples, one encounters new sets of experimental problems that may entail an initial, relatively steep learning curve. These difficulties originate particularly from the fragility of the weakly scattering aggregate paired with the dilute nature of the biochemical or cellular dispersion. Often, the Raman scattered intensity from these samples can be increased by carefully peileting the biological suspension using ultracentrifugation techniques. Since the overtone region of water, the usual medium for biological samples, absorbs radiation from both the Rayleigh signal at the exciting wavelength of the Nd:YAG laser and the longer wavelength Raman scattering from the sample, reproducible temperature measurements and temperature control become significant concerns. In these cases one appeals to internal temperature calibrations, use of deuterium oxide (D20) as a solvent (since absorptions of the laser exciting wavelength and Raman scattered photons are minimized), manipulation of incident laser spot size and the use of fiber optic bundles to carry the exciting and scattered radiation. In the present discussion we briefly cite some of the experimental approaches we have developed and experiences we have encountered in adapting near-infrared FT-Raman spectroscopy to the more challenging biophysical and biochemical systems amenable to vibrational analysis. We emphasize here the determination of the spectra of membrane assemblies and membrane related materials; in particular, we elucidate the interaction of several polyene antibiotics, including amphotericin A, amphotericin B and nystatin, with a model membrane system composed of dipalmitoylphosphatidylcholine bilayers.
The Los Alamos Fourier-Transform Spectrometer: Applications To Molecular Spectroscopy
Byron A. Palmer, Robin S. McDowell
We outline design considerations and operating characteristics of the Los Alamos Fourier-transform spectrometer, a state-of-the-art instrument operating from 200 nm to 20 μm with a resolution of 0.0026 cm-1 and very high wave number and intensity accuracy. Recent work in molecular spectroscopy carried out with this instrument will be discussed, including N2+ spectra obtained in inductively-coupled plasmas; high-temperature spectra of diatomic molecules of astrophysical interest; high-resolution rovibrational fine structure; and Fourier-transform Raman spectroscopy of species in expansion-cooled gases.
The Role Of Infrared Spectroscopy In Quality Control And Chemical Process Analysis - New Applications For FT-IR Spectrometers
John Coates
FT-IR spectrometry has evolved from the research tool of the mid 1970s into a simple push-button technique for the routine testing laboratory in the late 1980s. This evolution has taken place in several stages, and has involved key developments in technology. There are at least three changes in the technology that have contributed - the development of rugged, compact spectrometers, the production of table-top computer systems, and the design of high-efficiency optical sampling accessories. The combination of these developments has not only extended the application of FT-IR technology into routine analysis, it has also opened the door for a potentially much larger opportunity, custom-designed instrumentation for product quality control and chemical process analysis.
PA-FTIR Detection Of External Lubricants In Styrenic Polymers
T. Kumar, K. E. Yock
A simple Fourier transform infrared (FTIR) method using Photoacoustic (PA) detection is used to detect external lubricants directly on the surface of styrenic resin pellets. This technique is non-destructive, requires no sample preparation and rapidly determines the lubricant chemical class. This rapid qualitative procedure significantly reduces the subsequent quantitative analysis time of unknown samples. The application of PA-FTIR and the advantages of applying spectral subtraction in identifying fatty acid and substituted fatty amide external lubricants on some styrenic resins will be presented.
FTIR In Fat Processing And Fermentation Technology
H. Sadeghi-Jorabchi, M. K. Hammouri, R. H. Wilson, et al.
The potential of Fourier Transform Infrared (FTIR) spectroscopy and attenuated total reflectance (ATR) techniques in fermentation technology and fat processing are discussed.
Automated Sampling Using The Qcircle ATR Cell: An Example
Frederick L. Baudais, Frank Wasacz
Specialization; optimization, and automation of analyses is becoming more prevalent. Demands are made on instrument manufacturers to provide total systems that include the spectrometer, the IR sampling device and the software to control both the FT-IR spectrometer and the sampling system. When combined together and calibrated, this combination gives answers and not just spectra. As a result, more integrated systems are being offered that include the sampling system together with a FT-IR spectrometer and software to provide answers. One such system is the QCircle cell in combination with a FT-IR spectrometer, the Bomem MB110 spectrometer, and software such as Bomem Calc.
FT-IR Analysis Of Oil Emulsions Used In The Cold Rolling Of Steel
K. C. Cole, A. Pilon, D. Noel
In the cold rolling of steel sheet, oil-in-water emulsions are used to provide lubrication and cooling. Both the concentration and the quality of the oil involved must be carefully controlled in order to produce an acceptable product. Current analytical procedures usually involve separation of the oil from the water, followed by analysis of the different components by various wet chemical and instrumental methods. In principle, attenuated total reflection FT-IR spectroscopy offers the possibility of obtaining much or all of the required information from one measurement made directly on the emulsion. This paper describes some preliminary results involving the use of ATR spectroscopy to determine the percentage of oil in a clean emulsion. Although the use of ATR for aqueous solutions is well known, its applicability to emulsions has been less widely studied. In particular, the heterogeneous nature of emulsions could cause problems not encountered with aqueous solutions.
Use Of The Diamond Cell In An Industrial Laboratory
R. L. Barbour, J. D. Stephens, D. G. Cameron
The traditional method for recording the IR spectra of solids has been KBr pellet transmission spectroscopy. This technique has several disadvantages: sample preparation time, matrix contamination, spectral distortion, ion exchange, a limited spectral range, scattering, loss of sample integrity during grinding, etc. In recent years, diffuse reflectance, ATR, photoacoustic reflectance, and external reflectance have been used increasingly, facilitated by the high SNR of FT instruments. In many cases, the diamond cell is an attractive alternative to all of these. The spectral range is -100 -1 to the UV, excluding the 2200-2000 cm -1 region. Spectral distortion, usually a great problem with inorganics, is greatly reduced as a result of sample homogeneity (from a spectral point of view) and refractive index matching. There is no matrix contamination: scattering, background slope, and all absorption bands are from the sample. There is no ion exchange. The sample size requirements are minimal. Finally, sample preparation requires the somewhat lost. but powerful, art of microscopic examination. In some instances, there may be sample orientation or pressure induced phase changes associated with the use of the diamond cell. A common misconception is that an IR microscope is needed to use the diamond cell. In fact, ~5 minutes will suffice without a beam condenser; 1 minute is all that is needed with one. In part, this is because one usually has excellent control of the optical thickness; with experience, the cell can easily be assembled to give bands in the 0.7-1.5 absorbance range, and making the sample thinner merely involves pressing the diamonds together. Given the above, the microscope should only be used for inhomogeneous samples as one loses all information below 700 cm-1, the region of greatest value when studying inorganics. We also note that the cell can readily be moved from a mid-IR to a far-IR bench. We have moved to the point where this is the dominant sampling technique, with ATR being the next most important. Diffuse reflectance and KBr pellets are seldom used. The cell has been used on inorganics (mid and far IR) including extremely small pure mineral samples selected by hand. It is also used for polymers, polymer inclusions, filter deposits, pure (and not so puce) organics, and general "what is this stuff" samples. Examples of a wide variety of analyses will be given.
Compositional Assurance Testing -A Systems Approach To Chemical Quality
Jack H. Hartshorn
Chemicals and chemical formulations are often extensively tested for purity, activity and conformance. However, in a surprising large number of cases these tests miss the point; in that the material has the wrong composition. Through human, mechanical or computer error the product is mislabeled or mischarged. These wrong compositions may still pass the control tests but will not work for their intended end-uses, i.e. they are 100% pure wrong stuff. In order to "error-proof" our producls, Du Pont has developed our "Compositional Assurance Testing System" (CATS ). If the sample is contaminated, mislabeled or mischarged the differences are immediately apparent because a "goodness of fit" is too large. The lot can then be rejected and the problem investigated. The system employs a Fourier transform spectrometer and special computer program. With it an operator can verify the composition of a raw mterial, intermediate or finished product in less than three minutes.
Fourier Transform Infrared Spectroscopic Studies Of Wheat In The Mid Infrared
Jill M. Olinger, Peter R. Griffiths
Official grain standards of the United States state that wheat may be divided into seven classes which are: Durum, Red Durum, Hard Red Spring, Hard Red Winter, Soft Red Winter, White, and Mixed.1 Most end uses of wheat involve converting the grain into flour through one of a variety of grinding methods. The quality of wheat-based products is often very dependent upon the type or class of wheat which was used to make the flour. Pasta products, for example, are made almost exclusively from the flour of durum wheats, which are the hardest of the wheats listed above. The highest quality breads are produced using flour from wheats classed as hard, whereas cakes, cookies and pastries are considered best when flour from wheats classed as soft are used. It is obvious then that the capability of determining the class of a particular wheat, especially with respect to hardness, is of economic importance to growers, processors, and merchants of wheat and wheat products. Hardness has been measured in many different ways 2-5 but, as of yet, no one method has become the method of choice. This paper reports on the use of principal components analysis (PCA) of mid infrared diffuse reflectance (DR) spectra of diluted ground wheats to aid in the classification of those wheats with respect to their hardness. The theory and mathematics involved in a principal component analysis have been described elsewhere.9
Timeresolved Ftir Difference Spectroscopy Applied To Ultrathin Layers Of Membrane Proteins
Klaus Gerwert, Georg Souvignier, Benno Hess
ΔTo get insight in the function of proteins on an atomic level is a challenge of life science today. By x-ray-structure-analysis the architecture of a lot of proteins was obtained at atomic resolution. In order to understand the function of these structures, time resolved methods have to be developed. Using the Laue method, time resolved x-ray-structure-analysis seems to become applicable in the future. But this technique only gives a snapshot of an activated protein state during a reaction. In contrast, time resolved FTIR difference spectroscopy is able to monitor reaction kinetics of single amino acid side chains, e.g. protonation changes of internal aspartic acid residues, and of conformational changes of the protein backbone (1)(2)(3). By this technique interferograms are taken in a rapid scan mode before and after initiation of the investigated process. Difference spectra are computed between absorbance spectra of the ground state and the activated state. The scantime T is determined by the velocity of the scanner Vscan and the spectral resolution Δυ: T = 1/2 1/Δυ l/vscan. For 8 cm-1 spectral resolutionn a scantime T of 10 ms is yielded. The repetition rate between two scans is 44 ms.
FT-IR Spectra And Normal Vibrational Analysis Of Bilirubin IX
Xiu-zhen Wang, Jin-guang Wu, Bao-zhu Yu, et al.
Bilirubin (C33H36N406) is a water insoluble breakdown product of hemoglobin. It is of biological importance. For example, it can bind with calcium ions to form calcium bilirubinates which are major components in human pigment gallstones. The identification of IR bands of bilirubin are incomplete and the band assignments by different authors have not coincided.
Development And Performance Of A Novel IR-ATR-Based Glucose Sensor System
Ch. Weigel, R. Kellner
FTIR-ATR-spectroscopy can be used to design an optical glucose sensing system. The building of an immobilized enzyme layer, via 3-Aminopropyltriethoxysilane (3-APTS) and glutaraldehyde leads to a stable glucose oxidase (GOD) film on a germanium crystal with a thickness smeller than the penetration depth of the IR-radiation (<0.5 um). The system measures the absorbance of the 1153 cm gluconic acid band and exhibits a good linearity (for glucose concentrations of 0.52 - 20 mM) with a correlation coefficient of 0.96.
FTIR Study On The Secondary Structure Of Mucin From Mucinous Cystadenoma Of The Ovary
Keng Shen, Paochen Wu, Weij in Zhou, et al.
The mucinous cystadenoma, a common benign neoplasm of the ovary, may sometime bring about a fatal outcome known as pseudomyxoma peritonei which is characterized by massive accumulation of mucinous substance in the peritoneal cavity, resulting in extensive adhesions, chronic progressive intestinal obstruction and finally death of the patient. Surgical approach to this condition proves to be a palliative procedure. Repeated operation can only remove part of the geletinous material and reaccumulation of mucus within 1-2 years after the initial surgery is almost a rule. In view of the benign histologic nature of the disease, chemotherapy, either systemic or intraperitoneal, and radiotherapy are generally ineffective in arresting the progression of the pathologic process and preventing the reaccumulation of mucus. Therefore, the only hope lies on the introduction into the peritoneal cavity some agents which may dissolve the accumulated mucin, relieve the intestinal obstruction, and consequently, prolong and even save the life f the patient. Based on this conception, sporadic articles by a few authors(1,2)ap-peared in the literature reporting their clinical experience with different mucolytic agents. However, some blindness would inevitably be involved in such investigations due to the lack of a comprehensive understanding of the chemical structures of the substance. The purpose of the present paper is to report our preliminary results of study of the secondary structures of mucin secreted by this special type of tumor.
FT-IR Investigations Into The Fluidity Of Lipopolysaccharide And Lipid A Membrane Systems
K. Brandenburg, U. Seydel
Lipopolysaccharides (LPS) are the major amphiphilic components of the outer membrane of Gram-negative bacteria. They are composed of a poly- or oligosaccharide portion being covalently linked to a lipid moiety called lipid A. LPS are also called endotoxins because of their ability to induce harmful effects in organisms. However, they also exhibit beneficial ('adjuvant') activity for example by stimulating the immune system and inducing the production of e.g. the tumor necrosis factor and interleukin 1. The mechanisms leading to a stimulation of the cells of the immune system should mainly be governed by the fluidity and/or the supramolecular structure of the LPS and lipid A assemblies interacting with the cell membrane. In this contribution we report on FT-IR measurements of the fluidity of various LPS and of some lipid A's, and on the influence of the concentration of divalent cations, pH and water content on this parameter. The LPS differ in the headgroup conformation/composition, i.e in the length of the sugar moiety. The lipid A's show variation in their acylation patterns.
An Infrared Study Of N-Methylacetamide On Solid Surfaces: A Model Molecule For The Peptide Group In Proteins
Bo Liedberg, Christer Tornkvist, Ingemar Lundstrom
Infrared reflection-absorption spectroscopy (IRAS) and attenuated total reflection (ATR) spectroscopy have been used to investigate the bonding characteristics of N-methylacetamide (NMAA) on solid surfaces with different surface energies. Infrared spectra of monomolecular layers on hydrophilic (clean) surfaces suggest that the -C=N- nature or dipolar form of the peptide bond partly remains on the surface because of hydrogen-bond interaction with surfaces hydroxyls or adsorbed water molecules, whereas no such interaction occurs on hydrophobic (alkyl-modified) surfaces. The results obtained for the hydrophobic surfaces indicate that the -C=N- axis of the peptide bond becomes more notable, a phenomenon which for protein molecules may lead to a loosening of the backbone structure and a more unstable conformation.
Geometrical Structure Information Of 5-Phenyl-2-Pyridinamine Derivatives By Means Of FTIR.
T. Visser, J. F.C. Stavenuiter, G. Zomer
Infrared N-H, O-H and C=0 absorption bands of N-substituted hydroxy-, acetyl- and acetoxy- pyridinamines and biphenyl amines have been studied. Band deconvolution has been applied to determine the presence of rotational isomers. Ortho methyl substitution and the position of the pyridine nitrogen atom are found to affect the orientation of the amino substituents.
Infrared Analysis Of Enzymes Adsorbed Onto Model Surfaces
Gloria M. Story, Deborah S. Rauch, Philip F. Brode III, et al.
The adsorption of the enzymes, subtilisin BPN' and lysozyme, onto model surfaces was examined using attenuated total reflectance (ATR) infrared (IR) spectroscopy. Using a cylindrical internal reflection (CIRcle) cell with a Germanium (Ge) internal reflection element (IRE), model hydrophilic surfaces were made by plasma cleaning the IRE and model hydrophobic surfaces were made by precoating the IRE with a thin film of polystyrene. Gas chromatography (GC)-IR data collection software was used to monitor adsorption kinetics during the first five minutes after injection of the enzyme into the CIRcle cell. It was found that for both lysozyme and BPN', most of the enzyme that was going to adsorb onto the model surface did so within ten seconds after injection. Nearly an order-of-magnitude more BPN' adsorbed on the hydrophobic Ge surface than the hydrophilic one, while lysozyme adsorbed somewhat more strongly to the hydrophilic Ge surface. Overnight, the lysozyme layer continued to increase in thickness, while BPN' maintained its initial coverage. The appearance of carboxylate bands in some of the adsorbed BPN' spectra suggests the occurrence of peptide bond hydrolysis. A Au/Pd coating on the CIRcle cell o-rings had a significant effect on the adsorption of BPN'. (This coating was applied in an attempt to eliminate interfering Teflon absorption bands.) An apparent electrochemical reaction occurred, involving BPN', Ge, Au/Pd, and the salt solution used to stabilize BPN'. The result of this reaction was enhanced adsorption of the enzyme around the coated o-rings, etching of the Ge IRE at the o-ring site, and some autolysis of the enzyme. No such reaction was observed with lysozyme.
CD FTIR Spectroscopy Of Induced Cholesteric Solutions
Bojidar Jordanov
Circular polarization attachments for FTIR spectrometers developed on the basis of totally reflecting prisms were used for circular dichroic (CD) measurements of solutions of optically active compounds in nematic liquid crystals (induced cholesteric solutions). Two types of measuring schemes are presented, The first one uses a separate collecting of the interferograms for left and right circular polarization of radiation while the second one provides alternating scans for the same polarization states with an immovable polarizer, Some attempts for recording VCD spectra by means of the described attachments are discussed.
Circular Dichroism Measurement Using Fourier Transform Interferometry
N. Ragunathan, L. A. Nafie, T. B. Freedman
The first measurements of circular dichroism (CD) using a polarizing Michelson interferometer (PMI) are presented. PMI-CD was observed for infrared electronic transitions in the rare-earth metal complex, praseodymium-L-tartrate between 2400-2000 cm -1. Following further improvements in instrumental technique, vibrational CD was measured for (-)-α-pinene in the region 1350 to 900 cm-1. Comparisons to previous infrared CD measurements of these molecules shows excellent agreement.
Vibrational Circular Dichroism Studies Of Interchain Hydrogen Bonding In Tripodal Peptide Molecules
M. G. Paterlini, T. B. Freedman, L. A. Nafie, et al.
Vibrational circular dichroism (VCD) has been used to determine the solution structures of three tripodal peptide molecules. The interchain hydrogen bonding is shown to be oriented in a clockwise direction (from C=0 to NH) by application of the coupled oscillator mechanism in the carbonyl stretching region. The carbonyls of the terminal Boc groups are found to be oriented in a counterclockwise direction. Open chain conformations and dimers are also present in solution and contribute to the VCD spectra with monosignate intensity that is interpreted using the ring current mechanism.
Magnetic Vibrational Circular Dichroism With An FTIR
Paul V. Croatto, Ryong K. Yoo, Timothy A. Keiderling
We have developed a bench for a FTIR-based instrument that enables us to obtain Magnetic VCD spectra on high symmetry molecules at higher resolution. Solution phase MVCD for a metalloporphyrin and rotationally resolved MVCD for gas phase CH4 are presented.
Vibrational Circular Dichroism Of Proteins
Petr Pancoska, Sritana C. Yasui, Timothy A. Keiderling
We have measured VCD spectra of more than 20 proteins in the amide I' region. These data show an enhanced sensitivity to the differences in these globular proteins as compared to UV.CD. Factor analysis correlates with the a and β composition.
Dynamic Infrared Linear Dichroism (DIRLD) Spectroscopy Of Human-Hair Keratin
Anthony E. Dowrey, Greg G. Hillebrand, Isao Noda, et al.
Dynamic infrared linear dichroism (DIRLD) spectroscopy is used to study time-dependent changes in human-hair keratin films under small-amplitude oscillatory strain. The amplitude and rate of submolecular reorientation observed are very dependent on the molecular environment of the functional group being probed. DIRLD spectra of keratin films are extremely sensitive to molecular-level changes induced by temperature, relative humidity, and the addition of hair-treatment actives. By using correlation analysis, DIRLD data can be represented in a two-dimensional infrared (2D IR) format to compare the reorientation rates of individual dipole-transition moments. 2D IR spectra provide a clear resolution enhancement of the naturally broad amide I and amide II IR absorbance bands. The net result is an improved molecular-level understanding of the mechanical properties of human hair and identification of factors affecting these properties.
Near-Infrared Spectroscopy With Fiber Optics And Chemometric Data Treatment
B. FeldhAuser, K. Meya, H. W. Siesler
Adjacent to the conventional mid-infrared (MIR) region (4000-400 cm-1) the near-infrared (NIR) region of the spectrum covers the interval from about 10000-4000 cm-1 (1000-2500 nm). Due to the limited qualitative aspects this wavelength range has so far been primarily applied for quantitative analysis of OH-, NH- and CH-functionalities. Recently, however, it has been recalled to the attention of spectroscopists by the introduction of fiber-optic probes for process-control and remote sensing in combination with chemometric data handling procedures for multicomponent analysis and identity control.
An FTIR-Vapor-Phase Flavor-Library For The Rapid Identification Of Unknowns In Complex Flavor Samples
G. Fischboeck, R. Kellner, W. Pfannhauser
With the increasing importance of GC-FTIR-spectroscopy as a complementary molecular-specific detection technique to GC-MS and the high instrumentation standard that could be reached in this field one can get dozens of interpretable, good quality IR-spectra well into the low ng-level using lightpipe-techniques [1].
Fourier Transform Near Infrared Spectrometry: Using Interferograms To Determine Chemical Composition
R. M. Hoy, W. F. McClure
Previous research conducted in this laboratory has demonstrated several advantages accrued by transforming near infrared spectra from the wavelength domain to the Fourier domain. Those advantages include: [1] smoothing wavelength domain data without loss of end points, [2] correcting for particle size phenomena encountered in solid sample analyses by simply omitting the mean term Fourier coefficient from the "retransformation process", [3] minimizing the multicollinearity problem prevalent in wavelength space, [4] generating wavelength-space derivatives from Fourier space without loss of end points, [5] performing band enhancements via Fourier self-deconvolution, [6] identifying sample type using Fourier vectors, [7] estimating chemical composition using only the first few Fourier coefficients, [8] cutting of computer storage requirements by more than 96%, [9] cutting of calibration time by more than 96%, hence [10] reducing the drudgery of maintaining calibrations. That the first 12 Fourier coefficients contain sufficient information to determine chemical constituents in many products has turned out to be a major advantage leading us to understand that the chemical absorption information in the wavelength spectrum of a sample obtained with an interferometer was also present in the interferogram.
IR Calibration Evaluation And Selection Using Monte-Carlo Methods
Mark A. Lovik, Mark L. Olson
Modem quantitative IR spectroscopy includes a wide repertoire of techniques including: K and P matrix methods, principal component regression (PCR), and partial least squares (PLS). The relative merits of these methods has been discussed in the literature, however their relative performance often depends on the specific chemical system studied. Further the relative performance of individual implementations of a single technique can vary. What is necessary is a common set of tools that can be used to examine every method in a consistent manner. This set of tools can then be used in selecting the most appropriate quantitative model for the specific chemical system studied. The use of Monte-Carlo methods as a common calibration selection tool, and as a calibration diagnostic tool is presented. For univariate calibrations, simple inspection of a calibration plot can be used to evaluate alternate calibration methods. Diagnostic information, such as the required instrumental precision and accuracy necessary for desired calibration tolerances, is a straightforward procedure. In the multivariate case, extracting the same information is less intuitive. Finding the limiting noise sources in multivariate calibrations is often not easy to determine. By applying gaussian noise to individual calibrations parameters, the degradation in calibration performance can be plotted as a function injected noise. These plots provide specific noise sensitivity information that is straightforward in interpretation even when the details of the underlying method are unknown. This approach is largely technique independent, allowing the comparison of dissimilar methods. The use of Monte-Carlo diagnostics are illustrated, for the major quantitative IR methods, using two different example data sets. The first is from a designed experiment quantitating xylene mixtures using precise gravimetric reference analysis. The second is a near infrared data set quantitating moisture and protein using standard reference methods. These data are used to demonstrate the utility of Monte-Carlo techniques in providing necessary information for reliable multivariate calibrations.
An Evaluation Of Instrumental Correction Factors For Infrared Absorption Concentration Measurements
Aslan Baghdadi
This paper presents an analysis of a large multilaboratory set of infrared spectra to investigate the possibility of self-calibration of infrared spectrophotometers. The spectra were obtained from a round-robin study conducted in the U.S., Europe, Japan and China to determine the conversion coefficient for the determination of interstitial oxygen in silicon by infrared absorption spectroscopy.' Accurate measurement of the oxygen content of silicon wafers destined for integrated circuit manufacture is required in order to properly design the fabrication process.2
Advances In FT-IR Mixture Searching
Daniel T. Sparks, Arthur Schlieper, John Peterman
A popular method for identifying an unknown substance is to mathematically compare its infrared spectrum with a library of reference infrared spectra. The spectra of the best matches are then visually compared with the unknown spectrum in an attempt to discern the identity of the unknown substance. The assumption here is that when a reference spectrum for the unknown is contained in the library, that spectrum will appear as one of the top "hits" in the search. There are numerous factors, however, which can invalidate this assumption. Impurities at relatively high concentration levels can cause many problems including peak shifts due to chemical interactions, spurious peaks arising from isolated impurity absorbances, and shifts in relative peak heights due to impurity bands which coincide with the substance of interest.
Artifacts In FT-Raman Spectroscopy
D. Bruce Chase
The rapid improvements in detector technology, interferometer optimization and filter technology have brought the sensitivity in FT-Raman spectroscopy to a point where spectra can be recorded quite readily from most samples. The limitation is no longer due to detector noise. Instead, the problem of spectral artifact lines has now become the primary concern. We have identified several general groups of spectral artifacts, some of which are sample independent.
Spectroscopy With Triangular Modulation
P. L. Polavarapu
A procedure where the variation of a physical property in time can be represented by a triangular wave is considered. This triangular modulation can be used in FTIR instruments operating in the step-and-integrate mode.
Phase Spectra And Phase Corrections In High Resolution Fourier Transform Spectroscopy
Mark C. Abrams
Proper phase correction determines the accuracy and quality of the spectral information obtained by Fourier spectrometry. The spectrum produced by Fourier transforming an asymmetric interferogram is a complex function and the process of phase correction rotates the imaginary part of the spectrum into the real plane producing a real spectrum that contains all the spectral information and an imaginary part that contains only noise. For two-sided interferograms improper phase correction produces a second-order error in the intensity of the spectrum. In one-sided interferograms, the antisymmetric component of the interferogram transforms into the imaginary part of the line profile, and phase errors can have a first-order effect on the line position. Practical examples of phase spectra and both corrected and uncorrected power spectra will be presented.
Effect Of Apodization On Phase Correction In FTC
Shi-fu Fan, Chun-jin Lin
The effect of apodization on phase correction in FTS was researched. The paper presents some analogous and spectral experimental results. It was proved that for Forman's method the most suitable apodizing function in phase correction is cosine function, the Happ-Genzel function is also good one, but the triangular function is worse.
Spectrum Estimation Of FT-IR Data With Sampling Errors
D. J. Gingras
In usual rapid-scan FT-IR systems [1], the sampled interferogram values are recorded at measured positions of the moving mirror, the latter being subject to errors. The laser signal used for generating the reference cosine interferogram, for example, suffers from slight frequency fluctuations due, among other things, to temperature variations. During the zero crossing detection, an error is also introduced due mainly to the background radiation, detector noise electronic noise and mirror drive fluctuations [2] (imperfect delay compensation between HeNe LASER signal and infrared amplification electronics) [3]. It is therefore important to investigate the impact of sampling errors upon the interferogram values. Note that only "soft" zero crossing detection error are here considered, that is, no extraneous detection happens but only a random shift of the zero crossing event being detected. In this paper we consider stochatic as well as deterministic error models. We exploit the fact that the output interferogram results from the average of several scans. Hence it is of interest to investigate the property of the first statistical moment of the interferogram values subject to errors as well as the impact on the related true spectrum to be computed. As stochastic models, we treat the additive uncorrelated normal noise, the correlated normal noise and the uniformly distributed noise. For the systematic error model involving multiple harmonics, we extend the work of Sakai [2] on monochromatic signal to the broadband case.
Applications Of Near Infrared Fourier Transform Raman Spectrometry
Norman A. Wright, K. Krishnan
The development of near infrared Fourier transform Raman spectrometry as an alternative to visible Raman spectrometry has generated a great deal of interest. The advantages ascribed to an interferometric system include increased throughput, wavelength accuracy speed of analysis and the potential for high resolution work. Near IR excitation also allows for the analysis of compounds which are highly fluorescent. Because of these advantages, FT Raman spectrometry is gaining awareness as an analytical tool.
Near-Infrared Hadamard Transform Spectrometry
A. P. Bohlke, R. M. Hammaker, W. G. Fateley
Hadamard transform spectrometry is a multiplexing technique that shares some of the advantages Fourier transform spectrometry offers (e.g. the Fellgett's, or multiplex advantage and the Connes', or frequency precision advantage). Hadamard transform spectrometry, using a liquid crystal electro-optic shutter array (LC-OSA) as a stationary Hadamard encoding mask, has proven itself to be a viable technique in obtaining Raman spectra in the near-infrared (NIR). This no-moving-parts spectrometer is capable of spectral addition and subtraction and can be easily coupled with fiber optics.
Optimization Of The Sample Technique For NIR FT Raman Spectroscopy
Bernhard Schrader, Andreas Hoffmann, Martin Tischer, et al.
Raman spectroscopy is a powerful complement to infrared spectroscopy due to experimental as well as theoretical aspects: However, 'classical' Raman spectroscopy is not commonly used. This is mainly due to the fact that the fluorescence of minute amounts of impurities, excited by the radiation in the UV or visible range can mask the Raman spectra completely. NIR FT Raman spectrometers' have several advantages. As exciting light usually the radiation of the Nd-doped YAG laser at a wavelength of 1064 nm is used. Problems with fluorescing samples are largely reduced. There is the 'throughput advantage' of the Michelson interferometer and its high wavenumber accuracy. However, the intensity of the Raman radiation is inversely proportional to the fourth power of its absolute frequency. Laser light fluxes larger by the ν4-factor of about 30 are necessary to achieve the same radiance of the Raman lines in the NIR compared to the visible region. This enhances the danger of pyrolysis of the sample. In order to reduce this danger the whole instrument should have the largest possible optical conductance. Interferometers are therefore appropriate when they are properly matched to a sample arrangement with maximal efficiency.
Fourier Transform Raman Spectroscopy In The Near Infrared - Industrial Applications And Limitations
H. F. Shurvell, F. J. Bergin
In the past the application of Raman spectroscopy as an analytical tool has been severely restricted by laser induced fluorescence. It has been demonstrated recently 1,2, that near infrared Fourier Transform Raman spectroscopy can offer a solution to this problem. Near infrared laser excitation energy is, in general, too low to excite fluorescence. Unfortunately, the scattered Raman intensity is inversely proportional to the fourth power of the wavelength. This leads to a reduction in intensity of a factor of 22 on moving from 514.5 nm to 1064.1 nm excitation. Also, near infrared detectors are orders of magnitude less sensitive than photomultipliers used in conventional Raman spectroscopy. Despite these restrictions the FT-Raman technique opens up new possibilities for Raman spectroscopy.
Fourier Transform Raman Spectroscopy In Industrial Research
Stephen P. Church
Considering the importance of Raman spectroscopy as an analytical technique it is perhaps surprising that Raman spectrometers are seldom encountered in industrial laboratories and that so little work has been reported on samples of commercial interest. At least part of the reason for this can be traced to the large capital cost and the labour intensive nature of the sampling procedures. Even more significant, however, is the problem of fluorescence which more often than not totally obscures the Raman signal. Because of these difficulties Raman spectroscopy has played largely a secondary role and the unique information afforded from the Raman process has not been fully utilised.
A New Industrial FT-Raman/FTIR Spectrometer
Herve Guy, Pierre Beauchesne, Henry Buijs
At the International conference on Fourier Transform Spectroscopy in 1985, the seed was sown for the development of FT Raman. After establishing a solid base for research applications as shown at the International Conference in 1987. The technique has now advanced to the stage of routine use in industrial product development.
The Sample Field In The Atr Experiment
E. H. Korte, B. Jordanov
In an ATR experiment, the sample interacts with a field rather than with a wave. This field is made up from three compounds; one of these is perpendicular to the interfacial plane, the two others are parallel to this and, additionally, parallel or perpendicular to the plane of reflection, respectively. Commonly, one deals with the individual amplitudes of the oscillating compounds only neglecting their mutual phase correlation. However, when taking these into account, one finds that within the sample, the electric vector rotates and its tip describes an ellipse. The orientation of the ellipse with respect to the three constituing field compounds and the ratio of its axes are determined by the angle of reflection and the ratio of the refractive indices of the crystal and the sample, respectively. Possible states of the field and their experimental use will be discussed.
Fourier Transform Spectroscopy Using Surface Electromagnetic Waves With Aperture Excitation
N Yu Gushanskaya, V. A. Yakovlev, G. N. Zhizhin, et al.
The surface electromagnetic wave (SEW) spectroscopy 1 with laser sources of the IR radiat on has demonstrated high sensitivity to the state of the surface. The measurements of SEW attenuation on the sample give the information about the sample conductivity, surface roughness and about the presence of oxide or adsorbate on the metal surface, especially If their absorption bands are in the spectral region where laser lines are available. High sensitivity of modern Fourier transform spectrometers allows to detect SEW excited by broadband source. We have used Fourier transform spectrometers FTS-20V (Digilab) and IFS-113 (Bruker) with liquid nitrogen cooled detectors (Hg-CD-Te). On the metal (Ag, Al, Au, Cu, V, Be) surface SEW were excited using aperture coupling. The experiment is schematically shown on the fig.1. IR radiation from interferometer was focused on the gap between the sample 3 surface and the screen 1 placed at the distance of the order of 100 μm. In such a way on the gap propagating along a metal SEW and bulk radiation above the metal are excited. SEW runs from the aperture coupler to the edge of the sample (this distance could be varied from 2 to 30 mm) and decouples into the bulk radiation on the edge. The second screen 2 above the edge cut the bulk radiation from the aperture coupler. If we change the distance between the screens it is possible to obtain SEW absorption coefficient at different frequences from the output intensity variation. Fig.2 shows SEW propagation length spectra for Au and Cu. For these metals and also for Ag 2 propagation length is proportional to the square of the wavelength as it is predicted by Drude model. For Al such dependence is valid in the oxide transperancy region, in the region 800-1000 cm -1 natural oxide film give absorption band shown on Oxide films are well recognizible also on Be and V. Thermal growth or oxide film was studied (rig.4).
IR Reflectance Properties Of Weakly And Strongly Absorbing Surface Films
Yu-Sze Yen, James S. Wong
In an external reflection measurement, the optical properties of a surface film can give rise to a variety of spectral behavior on metallic and nonmetallic substrates. The diversity of behavior can be explained by the presence of transverse optical (TO) and longitudinal optical (LO) bands of the film in the infrared region. The excitation modes associated with these bands are directional with respect to the plane of the surface. Spectral interpretation is facilitated by understanding the roles of the TO and LO bands in reflectance spectra, the substrate selection rules for the appearance of these bands, and the relationship between the TO and LO frequencies. We will show that weakly absorbing films have a simpler optical behavior than strongly absorbing films.
Surface Characterization Of Cold-Rolled Steel By Grazing-Angle Reflection-Absorption FT-IR Spectroscopy
A. Pilon, K. C. Cole, D. Noel
Residues from the oil-in-water emulsions used in the cold-rolling of steel are responsible in large part for an undesirable film of contamination sometimes found on the steel surface, even after the annealing stage. This contamination can have significant effects on the adhesion and corrosion resistance of paint coatings subsequently applied to the surface. The object of the work reported here was to determine the potential of grazing-angle reflection-absorption FT-IR spectroscopy for qualitative and quantitative analysis of the residues left on the surface.
Multi-Spectral Microspectroscopyâ€"Goals and Progress
Robert G Messerschmidt
The practice of microspectroscopic analysis now spans the complete optical spectrum. The most recently popular of these measurements is the mid-infrared region where transmission, specular reflection and diffuse reflection measurements are performed with a microscope apparatus. Also, renewed and widened interest in micro-Raman spectroscopy has been brought about by the recent FT-Raman work, whose key benefit is the fact that the measurement is performed in the near-infrared region. Here, fluorescent interference is minimized. In the ultraviolet and visible regions of the spectrum, absorption and fluorescence measurements with microscopic apparatus are well developed. Currently, if one wishes to make use of all of these optical microspectroscopies, he must buy several different microscope/spectrometers, optimized for the particular measurement and type of specimen. Interestingly, there need be little difference in the microscope portion of these aparrati for the different measurements. This paper will discuss the evolutionary steps necessary to design a combined multi-spectral microspectrometer. What is to be gained is not only a cost savings, but also the ability to use the pieces of data collectively, improving the robustness of both quantitative and qualitative types of measurements.
Applications Of Image Analysis For Infrared Microspectroscopic Detection Of Contaminants On Microelectronic Devices
Kenneth J. Ward
The use of infrared microscopy imaging for location and identification of contaminants on microelectronic devices is discussed. Several methods for reconstruction of images from the spectrum acquired at each pixel were compared. Peak-height and peak-integration methods require prior knowledge of the contaminant to narrow the spectral region of interest. These frequency-limited methods performed better than full-spectrum methods. When full-spectrum methods must be used, Gram-Schmidt reconstruction performed better than integration.
Micro-FTIR As A Stress Probe For Ceramic Materials
James W. Rydzak, W. Roger Cannon, Maarit Hanninen
A method to measure stress in ceramics has been developed using an FTIR equipped with an infrared microscope. The method, developed with sapphire a a model ceramic materfal, involves calibration of small shifts in the 630 cm -1 band. A differential technique using spectral subtraction was developed to accurately measure the shifts (0.1-0.4 cm'). A four point bending apparatus was built to induce variable stresses in the surface of the sapphire. Ttle amount of stress has been correlated with the measured shift in the 630 cm 11absorbance band. The technique has been automated using a computer controlled mapping stage. Stresses near a crack in a sapphire sample have been profiled. This non-destructive technique has applications as a tool to help understand and improve mechanical properties of polycrystalline ceramics, composites, and optical fibers.
Applications Of Microspectroscopy In The Near-Infrared Region
Matthew J. Smith, Richard T. Carl
The technique of infrared microspectroscopy has numerous applications in many fields including materials science, forensics, contamination analysis and biological science. The majority of these applications have been in the mid-infrared since using different spectral ranges in an FT-IR spectrometer often involve modifications to the interferometer, source and detector. However, recent advancements in infrared instrumentation have allowed rapid spectral range changes to become routine. As a result, near-infrared microspectroscopy is now a viable technique.1 The principle advantage of near-infrared microspectroscopy is the ability to analyze samples which are totally absorbing in the mid-infrared region. Most near-infrared absorbances are due to overtones or combination bands of fundamental bands and are typically one to two orders of magnitude weaker than their corresponding fundamental transitions. Thus, transmission analysis in the near-infrared can be carried out on many samples which are otherwise too thick for transmission analysis in the mid-infrared.
Infrared Microscopy In An Industrial Analytical Laboratory
A. W. Strawn
This paper describes the chemical identification of solid samples in the size range of 8-250um in diameter. The samples are usually inhomogeneous and range from polymer inclusions to fibres. While scanning electron and optical microscopy are usually the first line of analysis for such samples, they cannot yield chemical identification when the sample is organic. A combination of infrared microscopy and spectral library searching provides a powerful technique in the industrial laboratory and examples are shown of polymer inclusions, laminates, fibres and filter deposits. The spectra were obtained using a Spectra-Tech IR Plan Microscope coupled to the external port of a Nicolet 5DXC FTIR spectrometer whose main compartment houses an MTEC Photoacoustic (PAS) Cell. The complementary facets of PAS and infrared microscopy are also highlighted.
Buffered Mobile Phases With Magic-LC/FT-IR
Raymond M. Robertson, James A. de Haseth, Richard F. Browner
The first demonstration is described of identifiable infrared (IR) spectra obtained from volatile buffer mobile phase using Monodisperse Aerosol Generator Interface Combining Liquid Chromatography with Fourier transform infrared (MAGIC-LC/FT-IR) spectrometry. Ammonium acetate, a volatile buffer, was used to buffer an 80:20 acetonitrile:water mobile phase to pH 5.0. Caffeine was deposited from this buffered mobile phase on a KBr window and the resulting spectrum compared favorably with a reference caffeine spectrum. The caffeine reference spectrum was obtained by depositing caffeine from a 100 percent water mobile phase.
Thin Layer Chromatography/Diffuse Reflectance Fourier Transform Infrared Spectrometry Of Coal Extracts
Mollie L.E. TeVrucht, Peter R. Griffiths
Coupling thin layer chromatography (TLC) with diffuse reflectance infrared spectrometry facilitates the analysis of coal extracts. Like coal itself, the extracts are composed of a complex mixture of many different components. After the easy, inexpensive TLC separation of the extracts into broad classes, the components are transferred simultaneously to a series of cups from which their diffuse reflectance spectra may be measured. The cups are packed with a chalcogenide matrix, which is transparent through much of the mid infrared. Because chromatographic resolution is preserved in the transfer, infrared spectra of all the separated component classes may be obtained. Studying various extracts of three different coals allows for investigation of the molecular differences between them thus providing valuable information concerning the structure of coal.
Preparation And IR Spectra On Some B-Diketone Complexes With Uranyl Ion
Nai Shi, Xiaochun Ding, Weijing Zhou, et al.
The β-diketonato complexes of uranyl ion with acetylacetone, benzoylacetone, dibenzoyl-methane and thenoyltrifluoroacetone, UO2A2-HA (HA=β-diketone ligands, and A=,β-diketonate anions), have been prepared and their infrared spectra were studied in the 4000-200 cm-1 range.
FT-IR Spectra Of Adducts Consisting Of Tetra-U-Acetatodirhodium (II) And Some Nitrogen-Containing Ligands
Weijin Zhou, Xiangyun Wang, Nai Shi, et al.
Nine new adducts consisting of tetra-μ-acetatodirhodium (II) and some nitrogen-containing ligands, i.e. Rh2(02CCH3)4L2 (L= POPOP,PP0,14-amidoantipyrine, ∝-naphthylamine, luminol, benzothiazole and hexahydropyridine) and Rh2(02CCH3)4L (L=tet b and 0-tolidine ), have been obtained. Infrared spectra in the range of 14000-M0 cm-1 of these adducts were studied with Nicolet 7199 B FT-IR spectrophotometer and results are briefed in the text.
Characterization Of Cobalt-Exchanged Zeolite A By DRIFT Spectroscopy
M J. Kappers, J. H. van der Maas, J. M, Chalmers, et al.
In-situ DRIFT spectroscopy has been succesfully used for the characterization of Co4Na4-A. Dehydration of the zeolite A appears to involve formation and breakdown of hydration complexes and hydrolysis. The position of cations and hydroxyl groups within the zeolite structure was derived from the adsorption of carbon monoxide and acetonitrile.
Investigations Of The Adsorption Of Carbon Monoxide On Platinum And Palladium Surfaces By In-Situ FTIR-ATR-Spectroscopy
E. Zippel, M. W. Breiter, R. Kellner
IR-ATR (Attenuated Total Reflection) spectra of CO adsorbed on thin, rough layers of both Pt or Pd deposited on Ge reflection elements display minly linear bonded CO bands (about 2050 cm-1). The bands for the bridged bonded species on Pt (about 1800 cm-1) are much weaker than those on Pd (about 1900 cm-1), the relative intensities and exact band positions depend obviously on the status of the metal surfaces.
Experimental And Theoretical Spectra Of Complex Ions In Oxochloroaluminate Melts
Mari-Ann Einarsrud, Martin Ystenes, Erling Rytter
Normally, metal oxides dissolve only slightly in chloroaluminate melts, and the oxochloroaluminate species are mostly formulated as Al0Cl2- or Al0+, depending on the acidity of the melt (1,2). In this work a metastable melt with composition NaAl20C15 has been prepared (At ca. 200°C the melt decomposes to NaAlCl4 (I) and AlOCl (s)). By comparing the IR-spectra of the melt and MNDO-generated spectra we have found strong evidences for the existence of complex ions in the melt.
FTIR Spectra Of Amorphous Silicates
Krystyna E. Lipinska-Kalita, Leonard M. Proniewicz
In the recent years growing interest has developed in studying of silicate glasses containing iron oxides. These glasses exhibit semi conductor characteristics and they are also of importance in several applications such as glass-metal composities and solar energy absorbers. The present study is a part of a research program in which the structure of silicate glasses is investigated by means of Fourier Transform Infrared, Raman and Mossbauer spectroscopy 1,2,3. The vibrational spectra of oxide glasses contain significant amount of encoded information potentially useful for elucidating glass structure as well as for interpreting physical properties of glasses.
Analysis Of Halogenated Dibenzo-P-Dioxins And Dibenzofurans Using Matrix Isolation GC/FT-IR
Charles J. Wurrey, Billy J. Fairless, Harry E Kimball
Reference gas chromatographic/matrix isolation/Fourier transform infrared (GC/MI/FT-IR) spectra have been recorded for the fifteen laterally chlorinated dibenzo-p-dioxins and dibenzofurans, the octachlorinated species of these two parent molecules, and the two 2,3,7,8-tetrabrominated compounds. The GC/MI/FT-IR technique provides isomer-specific spectra of these compounds, and detection limits for these substances using this method range from several hundred picograms to approximately one nanogram.
Examinations Of The Matrix Isolation Fourier Transform Infrared Spectra Of Organic Compounds.
W . M. Coleman III
Matrix isolation Fourier transform infrared spectra (MI/FT-IR), mass spectra (MS), carbon-13 Nuclear Magnetic Resonance (13C-NMR) spectra, condensed phase infrared spectra and vapor phase infrared (IR) spectra are presented for a series of terpene compounds. Subtle differences in positional and configurational isomers commonly found with terpenes could be easily detected by the. MI/FT-IR spqctra. The results are comparable in some aspects to those obtainable from IJC-NMR and thin film IR, however, most importantly, they are acquired at the low nanogram level for MI/FTIR as compared to the milligram level for the other techniques. These results represent an advance in the technology available for the analysis of complex mixtures such as essential oils containing terpene-like molecules.
Ftir Spectrum Of The N4+ Molecular Ion Trapped In Solid Neon
Marilyn E. Jacox, Warren E. Thompson
In studies of the codeposition at 4 K of a Ne:N2 = 100 or 200 mixture with a beam of neon atoms excited in a microwave discharge, a weak to moderately intense absorption at 2237.6 cm-1 can be assigned to the N4+ molecular cation. Earlier mass spectrometric studies had determined that N4+ is bound by approximately 23 kcal/mol with respect to N2 + N2+. Both ab initio calculations and electron spin resonance observations have indicated that N4 has a linear structure in its ground state. The analysis of the FTIR spectrum is also consistent with a linear structure. The sensitivity of the Bomem DA3.002 FTIR instrument used for these studies is sufficiently great for detection of the high frequency symmetric stretching absorption of several of the noncentrosymmetric isotopic species of N4+. A least squares force constant fit to the isotopic data provides a satisfactory assignment for all of the observed peaks.
Elucidation Of The High Temperature Oxidation Mechanism Of A Polybenzimidazole Through FT-IR Studies Of Isotopically Labeled Materials.
J. J. Rafalko, E. Chenevey
FT-IR studies of the oxidation of carbon-13 labeled [poly-2,2' (m-phenylene)-5,5' bibenzimidazole], PBI, and of the reactions of PBI in oxygen-18 environments were conducted to evaluate a previously proposed mechanism (1,2). A tentative oxidative degradation mechanism had been proposed primarily on the basis of mass spectral analyses of gaseous decomposition products, comparisons with model solution oxidation studies (1), and limited infrared analysis (2). It was postulated that initial attack on PBI occurs at the imidazole N-H. Abstraction of the N-H hydrogen by oxygen produces radicals. Oxygen reacts with these species to form quinoid type structures in the rings attached to the imidazole. These intermediates then break down into acids and eventually into aromatic nitriles and gaseous products. Again, only the nitriles and gaseous products were observed in the polymer studies.
Understanding The Interfacial Structure Of Aqueous Phospholipid Monolayer Films Via External Reflection FT-IR Spectroscopy.
Melody L. Mitchell, Richard A. Dluhy
Monolayer films of dimyristoyl-phosphatidic-acid (DMPA) at neutral and basic pH exhibit first-order phase transitions in their pressure-area curves. In situ external reflection FT-IR studies in the CH, stretching bands over this phase transition region exhibit a --6 cm-1 shift similar to that observed in previous studies of dipalmitoyl-phosphotidylcholine (DPPC)1. The acid form of DMPA at pH 3.0 does not exhibit the first order phase transition, but a ~1cm-1 frequency shift is observed in the liquid condensed phase and is also present in the neutral pH form. A solid-solid phase transition is proposed. Examination of the polar headgroup region (1300-960 cm-1)for acidic, neutral, and basic forms of DMPA give characteristic bands of each protonation state of PO3.
The Shift Of Gallstone Components Detected With FTIR
Zhi Xu, Xiaosi Zhou, Fuan Liu, et al.
Pigment gallstone is much more prevalent in China than that in the western countries. According to clinical observations, there are three developmental steps: sludge, soft concretions, and, at last, consistent stones. In the animal model of guinea pigs, in which pigment gallstones were induced by partial ligation of the common bile duct (CBD), the similar course occurred. Amorphous sludge was found in animals sacrificed in one (2 animals) and three (3 animals) weeks after the CBD ligation; two soft concretions with spherical shape and 1 to 1.5 CM in diameter were found in an animal seven weeks after ligaton.
FT-IR Studies Of Plasma Protein Behavior On Biomaterial Surfaces
Krishnan K. Chittur, Corazon A. Steginsky
Protein adsorption has been recognized as one of the early events in blood-biomaterials interactions. This interaction has been characterized by investigations that include studies of the kinetics of adsorption, adsorption isotherms, protein displacement from surfaces and interaction of platelets with adsorbed protein layers. Inspite of the rather large number of studies, we have a very limited understanding of what contributes to the failure of many of the biomedical devices.
Conformational Change During Modification Of Creatine Kinase By Iodoacetamide: A Resolution Enhanced FT-IR Analysis
Lin Yingzhang, Zhou Junmei, Xu Zhenhua, et al.
FTIR and Raman spectra, resolution enhanced by second derivative and deconvolution techniques, have been used for studying protein secondary structure 1,2. A subtle conformational changes related to solvent denaturation and chemical modification can be distinguished. It has been shown that Raman spectroscopy combined with second derivative techniques and hydrogen-deuterium isotopic exchange can be successfully applied to identify he subtle comformational differences in creative kinase(EC 2.7.3.2)3.
Fourier Transform Infrared Spectroscopy Demonstrates The Reactivity Of The Protonated Carboxyl Group Of The Acid Salt Of Calcium Bilirubinate.
R. D. Soloway, J-G Wu, D-F Xu, et al.
Calcium bilirubinate is a major salt in pigment gallstones. Bilirubin IX (H2BR) is a tetrapyrrole with 1 propionic acid side chain on both the B and C rings. A striking feature is the strong intramolecular hydrogen bonding of both carboxyl groups as determined by x-ray diffraction. This greatly reduces aqueous solubility. Much less is known about the structure of the salts of calcium bilirubinate since single crystals have not been formed. One or both carboxyl groups of bilirubin may coordinate with calcium in stone, forming the acid or neutral salt.
FT-IR Study On Calcium Ion Binding To Bilirubin
J-G Wu, R. D. Soloway, D-F Xu, et al.
After formation of either the acid or neutral salt of calcium bilirubinate, decrease or disappearance of bands indicated that calcium is coordinated to bilirubin via its carboxyl oxygens and pyrrole nitrogens, changing the conjugated structure of the molecule.
FTIR Analysis Of Cytochrome Bs In H2O And D2O
Peter W. Holloway, Henry H. Mantsch
The application of infrared spectroscopy to biological samples has been made possible largely by the advent of FTIR. The advances in instrumentation which have allowed this application are well documented, however, there are still some barriers to the full utilization of this technique for biological samples such as proteins. The general objectives are to obtain spectra in the 1700 - 1600 cm -1 region, where the Amide I band is located. This broad, generally featureless, band is a complex composite of bands which are characteristic of specific types of secondary structure in the protein 1. The problems to be overcome fall into several categories. The need to work in aqueous solutions, where water has a very large absorption band at 1650 cm4, has been circumvented to a large extent by working in D20, although it is still necessary to employ short path length cells, as the absorbance of the H-O-D overlaps both the Amide I and Amide II regions. In spite of the similarity of D20 and H2O, there are still advantages to obtaining spectra in both solvents as in D20 the accessible N-H groups in the peptide bonds will undergo H->D exchange. A comparison between spectra obtained in the two solvents will therefore give information on solvent accessibility of the peptide bonds in the different types of secondary structure and will also assist in assigning bands to particular secondary structures. Coupled with this requirement of short path length cells is the tendency of proteins to denature on surfaces. This requires that demountable cells be used and these cells, especially with 6 - 50 μm spacers, have a variability in path length from sample to sample, and especially from sample to the solvent blank which makes subtraction of the solvent blank very difficult. This problem of solvent subtraction is most acute when H2O is the solvent as here the high solvent absorbance is coupled with the smaller, and more variable, path length. Once the sample spectrum minus the solvent has been obtained the broad Amide I band has to be subjected to some type of enhancement procedure, usually Fourier self-deconvolution2, in order to resolve the bands due to particular types of protein secondary structure. Both the solvent subtraction and the deconvolution are somewhat subjective and open to criticism. In this report we demonstrate that reproducible deconvolved spectra can be obtained in both D20 and H2O.
A FT Spectral Study Of The H-Bond In Galanthamine
Z. Burgudjiev, M. Grinberg
The hydrobromide of the alkaloid galanthamine plays an im-portant role as a medicine in curing polyomelite as well as some diseases of vegetative nervous system. Its spectral properties are investigated by means of IR /1/, UV /2/ and fluorescent spectra /3, 4/ mostly in order to determine its quantity in solutions. Information about the molecular structure of galanthamine is obtained mainly by NMR /5/ and X-ray spectroscopy /6/. In this connection an interesting, but not solved today problem is arising about the existence of H-bond in galanthamine solutions and making more clear this problem is the subject of this work. A Bruker FR-IR spectrometer with termostated cuvette and a Bomem FR-Raman spectrometer are used. The spectral region between 3400 and 3700 cm-1 is considered. The existence of an intramolecular H-bond in galanthamine molecule proved by NMR /5/ and dispersive IR spectra /7/ is confirmed here on the base of obtained FR-IR and FT-Raman spectra. An attempt is made to calculate the H-bond energy. The intermolecular H-bond forming dimers in solutions as accepted in /5/ after NMR study, but not confirmed by dispersive IR spectroscopy /7/, is investigated here by means of temperature depending spectra.
Temperature Dependences Of The Infrared And Circular Dichroism Spectra Of Ribonuclease A And Troponin C
Tatsuyuki Yamamoto, Masaru Tanokura, Mitsuo Tasumi
Temperature dependences of the infrared and CD spectra of bovine pancreatic ribonuclease A and bullfrog skeletal muscle troponin C have been examined. In order to extract information on the secondary structure changes of these proteins from their infrared spectra, the methods of difference spectrum and Fourier-self-deconvolution have been applied. Both the infrared and circular dichroism spectra have confirmed that ribonuclease A undergoes thermal denaturation at 60°C in a typical manner. On the contrary, calcium-free troponin C shows gradual spectral changes with increasing temperature, indicating the absence of drastic conformational changes. No denaturation seems to take place for calcium-bound toponin C even at 80°C.
VCD Spectrum Of 6,8-Dioxabicyclo[3.2.1]Octane: Comparison Of Experimental And Model Spectra
Thomas Eggimann, Nan Ibrahim, Hal Wieser
We report the measurement of the vibrational circular dichroism (VCD)1 and infrared absorption spectra of 6,8-dioxabicyclo[3.2.1]octane in the region 800 to 1500 cm-1. The observed bands are assigned with the guidance of a scaled ab initio 3-21G force field. VCD and absorption intensities were calculated using the fixed partial charge (FPC), charge flow (CF), and atomic polar tensor (APT) models.1 FPC yields correct signs but low absolute intensities for most of the observed VCD bands. Introduction of one CF parameter which allows charge flow along the C-0 bonds improves the FPC results remarkably and brings them close to the corresponding observed and APT intensities.
Vibrational Circular Dichroism Of Simple Chiral Molecules In The Gas Phase
T. B. Freedman, K. M. Spencer, C. McCarthy, et al.
Mid-infrared FTIR vibrational circular dichroism (VCD) of two exceptionally simple chiral three-membered ring molecules with C2 symmetry, (S,S)-oxirane-2,3-2H2 and (S,S)-cyclo-propane-1,2-2H2, have been obtained in the gas phase at 1 and 4 cm-1; resolution. The signs and relative intensities of the prominent VCD bands can be understood in terms of coupled C*H or C*D motions.
FTIR Vibrational Circular Dichroism Of Oligopeptides Related To Polyproline
R. K. Dukor, T. A. Keiderling
Vibrational Circular Dichroism (VCD) data can be routinely measured by FTIR. On our FTIR VCD instrument it is possible to obtain a spectrum where baseline correction is accomplished with solvent only. Such capability is important for measuring biological systems. Several polypeptides that have been assigned to be in 'random coil' conformation all give an amide I VCD pattern which has the same sign and bandshape as poly-L-proline II but a smaller magnitude. This is consistent with a previous proposal by Tiffany & Krimm that the 'random coil' conformation of charged polypeptides actually has a significant local ordering in the form of a left-handed extended helix. To investigate this problem further we have studied the effects of temperature and chain length on the VCD bandshape of this conformational type. The latter studies were done with (Pro)n, n=2-7. Our results indicate that even at the level of (Pro)4 the VCD spectrum has the same bandshape, sign and intensity as found in the 'random coil' poly-L-glutamic acid spectrum. Data on various 'random coil' systems will be compared to the model studies we have done.
Characterization Of Langmuir-Blodgett Layers And Other Ultrathin Films Using Polarization Modulated Ftir Spectroscopy
T. Buffeteau, B. Desbat, J. M. Turlet
Polarization Modulated Reflexion Absorption Infra-Red Spectroscopy (PM-IRRAS) is a very sensitive method to analyse in situ and non-destructively adsorbates and ultrathin molecular films, as for instance, a single Langmuir-Blodgett (LB) layer. Extended experimental conditions and preliminary results demonstrating this high surface absorption detectivity, have been already published 1-3. In this communication, we want to stress on two important points that have been very often neglected : the quantitative analysis of PM-IRRAS spectra and the extension of this method to nonmetallic substrates.
Application Of Step-Scan Interferometry To Dynamic Infrared Spectroscopy
Richard A. Palmer, Christopher J. Manning, Jeffrey A. Rzepiela, et al.
Most commercially available FUR instruments operate in the rapid-scan mode. In the rapid-scan mode, the moving mirror of the interferometer is scanned repeatedly at a constant velocity, thus every wavelength present is modulated at its own Fourier frequency. The sum of the sinusoids for all wavelengths in the bandwidth of the instrument is the recorded interferogram. Repeated interferograms are usually coadded before transformation in order to achieve the desired SNR. However, the rapid scan mode is difficult to apply to dynamic systems, especially when the relaxation time of the system is in the range of the commonly used Fourier modulation periods.1 This convolution of the temporal aspects of the experiment with the spectral multiplexing is avoided, and most of the advantages of (rapid-scan) FT interferometry are retained, by proper application of step-scan techniques of data acquisition. In the step-scan mode the moving mirror is stopped at, or vibrated about, each data collection point and data can be collected either in the impulse/response mode at discrete intervals of time following the impulse or in the synchronous modulation mode as in-phase and quadrature components of the signal with respect to the modulation. This modulation can be imposed either on the IR beam, or the sample's absorption, reflection or emission can be modulated by exciting the sample itself. For dynamic IR spectroscopy, the step-scan FUR mode simplifies data collection and allows relatively simple retrieval of the signal phase separate from the instrument phase. Applications illustrating how these advantages are realized in classical time-resolved spectroscopy and in phase-resolved two dimensional IR spectroscopy are illustrated below. The design principles of the step-scan interferometer used for the experiments described in this paper are covered in the paper by Manning, Palmer and Chao, in this volume (see also reference 2). In brief, the instrument is a modified IBM-IR-44; stepping is controlled by the application of a synchronous modulation to the moving mirror position and use of lock-in feedback loops to monitor the resulting modulation of the HeNe laser interference pattern. The mirror position is electronically and viscously damped. Data are collected at intervals corresponding to integral multiples of λ/4HeNe; depending on the desired free spectral range, at stepping paces as slow as desired and up to 10 Hz. The design is adapted from that originally published by Debarre, Boccara and Fournier.3
Rheo-Optical Fourier-Transform Infrared Spectroscopy Of Polyamide Elastomers
S. Dekiert, H. W. Siesler, J. Lohmar
The potential of rhea-optical Fourier-Transform infrared (FTIR) spectroscopy is demonstrated with reference to the characterization of segmental orientation during cyclic elongation-recovery procedures of poly(ether-ester)amides based on chain-extended polyamide 12 (hard segments) and oligotetrahydrofuran (soft segments). The rheo-optical data show that the soft and hard segments deform by different orientation mechanisms. Thus, the soft segments exhibit positive chain alignment during loading and desorientation upon unloading. The deformation of the hard segments is characterized by an initial transverse orientation with a subsequent reorganization of their morphology.
FT-IR Emission Spectroscopy As A Tool For Studying Thin Films And Thermal Changes In Samples
Senja V. Compton, Jay R. Powell, David A.C. Compton
Infrared emission spectroscopy has been used routinely to study samples at high temperatures, such as rocket plumes. The designs of modern FT-IR instruments and a new emission accessory having high optical throughput, now allow the observation of emission spectra at much lower temperatures than previously. This greatly enhanced sensitivity to emission energy can be used routinely to either record spectra at room temperature, or obtain information about very thin films.
Applications Of Fourier Transform NIR/Raman
R. W. Hannah, A. Ganz, D. Schiering, et al.
A NIR Raman accessory has been designed for use with a Perkin-Elmer Model 1700 Fourier Transform Spectrometer. The design does not interfere with application of the instrument for normal mid-infrared spectroscopy. In order to demonstrate performance, a number of different types of samples and analytical problems have been considered. These include structure-spectra correlations, pharmaceuticals, polymers, highly colored and fluorescent materials, and sampling.
FT-Kaman Spectroscopy And Pulsed Excitation
D. Bruce Chase, Terry Gustafson
It has been previously shown that equivalent results are obtained in FT-Raman spectroscopy using both pulsed and CW excitation if the following two criteria are met. 1) The pulse repetition rate must be significantly higher than the detector roll-off, and 2) The pulse length must be long enough so that interferometer resolution is not degraded. The results using a mode locked Nd/YAG laser operated with various pulse widths will be shown. The operation with pulsed excitation is necessary if one wishes to do a pump-probe Raman experiment for the detection of excited state Raman spectra. The initial results of such an experiment will be shown.
Eliminating Ftourescence Interference With Near-Ir Fourier Transforn Raman Spectroscopy
Francis J. Purcell
Fluorescence interference has been a major impediment to obtaining Raman spectra from many samples illuminated by laser at visible wavelengths. Fourier-transform (FT) Raman spectroscopy in the near-infrared eliminates the problem of fluorescence background, and automated systems designed to apply this advantage in industrial environments make it possible to accurately and conveniently analyze almost any material. FT-Raman data also complements information acquired via FT-IR absorption analysis. Taken on a system combining FT-Raman and IR capabilities, spectra of samples that include alcohols, polymers and amino acids demonstrate the practical utility of these techniques for industrial and research applications. In addition, such instrumentation offers data acquisition speed comparable to conventional Raman analysis, as well as throughput and multiplex advantages. Samples may also be illuminated at higher power in the infrared without rotation to prevent thermal damage.
Sampling Methods In FT-Raman Spectroscopy
Philip R. Brierley, Robert J. Rosenthal
The extension of the Raman technique to the use of excitation wavelengths in the near infrared shows much promise, especially for samples exhibiting strong fluorescence when excited by the visible lasers used in dispersive Raman instrumentation. The dependence of the Raman signal on the fourth power of the excitation wavelength has precluded the common use of near infrared excitation due to signal to noise considerations.
TGA/FT-IR Evolved Gas Analysis Using Target Factor Transformation
David A.C. Compton, Frederick Cahn
A series of spectra have been recorded during a varying evolution of gases from a thermogravimetric analyzer. The composition of the gas mixture has been analyzed by target factor transformation, in order to test whether this procedure will be able to identify the components without operator intervention. The major components evolved during the weight loss were identified, which demonstrates that this approach is valid.
Phase Spectroscopy Of Surface Electromagnetic Waves Using Fourier Spectrometer
L. A. Kuzik, V. A. Yakovlev, G. N. Zhizhin, et al.
The surface electromagnetic wave (SEWS spectroscopy has shown high sensitivity to the state of the surface . The measurements of SEW attenuation andphase retardation during SEW propagation on the sample allow to obtain Ihe optical constants of surface layer or oxide on the metal. Up to now phase spectroscopy used laser sources of radiation, thus the interference measurements were done only in the spectral region where laser lines are available. To apply phase spectroscopy or SEW to the surface analysis widely it is necessary to expand the spectral region where they are studing. High sensitivity or modern Fourier transform spectrometers allows to detect SEW excited by broadband source. We have used Fourier transform spectrometers FTS-20V (Digilab) and Michelson-110 (BOMEM) with liquid nitrogen cooled detectors (Hg-Cd-Te). On silver surface SEW were excited using aperture coupling. The experiment is shown on the fig.1 . IR radiation from interferometer was focused on the gap between the sample 3 surface and the screen 1 placed at the distance of the order of 100 μm. In such a way on the gap propagating along a metal SEW and bulk radiation above the metal are excited.
Regular-Reflection IR Spectroscopy Of Historical Varnishes
E. H. Korte, H. Staat
Regular-reflection IR spectroscopy is revisited in view of non-destructive in-situ analyses of historical varnishes. The angle dependence of the average level of reflectance as well as of the sign and the amplitude of the dispersion-like features the reflection spectrum consists of, are discussed. The close relation between the reflectance spectrum at the Brewster angle and an absorbance spectrum is illustrated by an experimental example.
Tribological Studies By ATR-Infrared Analysis
G. A. Kohler, G. S. Deeb, W. A. Peters, et al.
Tribological studies of surface interaction phenomena involving friction, lubrication and wear are enjoying a new renaissance due to recent material developments and renewed concern with material and energy conservation. An understanding of surface and interfacial chemistry is essential if we are to decrease friction between contacted surfaces.
FTIR Investigation Of Thin Organic Layers On Float Glass: Applications In Wettability And Adhesion.
J-M Berquier, A-C Fernandes, P. Chartier, et al.
A FTIR technique (specular reflection with an incidence angle of 60° and light polarized parallel to the surface) is used to obtain information on thin organic layers on float glass. Two applications are described. 1) A spectrum of a self-assembled monolayer of octadecyltrichlorosilane on the glass surface is shown in the area 3000-2800 cm-1. Due to the monolayer orientation only -CH2- stretching vibrations are visible. 2) Hot-pressed polyurethane is peeled off from the glass : spectra of polymer residues on glass are obtained and the failure is shown to be cohesive.
Enhanced Polymer Discrimination By Infrared Microtransmission And Microreflectance Spectroscopy
K. Krishnan, P. J. Stout, S. L. Hill
The infrared microsampling technique has dramatically influenced the polymer analysis field. Polymeric single fibers and small particles are obvious applications for qualitative microanalysis. Recent advances in methodology have addressed the characterization of otherproperties of polymeric materials whose size exceeds that of traditional microsamp pleps (10-50 micrometers). Specific layers of a laminate film may be identified by analyzing a thin microtome cross-section by microtransmission. The influence of stretching upon a polymer film may be studied in-situ by polarized microtransmission. The mechanism of polymeric deformation may be defined as a function of the degree of draw or by the satial distribution of relaxation. Molded polymer products may be non-invasively characterized by microreflectance analysis. Automated spectral imagin experiments may be performed upon many polymeric systems to associate the disg tribution of specific infrared absorptions to visually-identified sample anomalies.
Reflection Spectroscopy With The FT-IR Microscope
William T. Wihlborg, John A. Reffner, Scott W. Strand, et al.
The FT-IR microscope is a versatile sampling accessory used to record IR spectra in either transmittance or reflectance modes and capable of obtaining data from microscopic sampling areas. Because the FT-IR microscope simplifies the collection of reflectance data it has renewed interest in reflectance spectroscopy. Moreover, the ability to see the specific sample and to obtain spectra from small areas makes it possible to differentiate the mode of the reflection data. Reflections can be specular, diffuse or reflection-absorption modes. These modes are not independent, but the sample and its surface geometry can cause one mode to dominate all others. With polished grains or single crystal faces, specular reflection is the dominate mode. Thin films on metallic reflecting substrates make reflection-absorption the major reflection mode. Diffuse reflection dominates when the surface is very rough or fine irregular particles are analyzed. Since the sample can be seen with the microscope, the reflection mode can be predicted by direct observation of the sample's surface. In this work, examples of reflection spectral measurements are presented to illustrate the versatility of the FT-IR microscope. Of particular interest is the first report of quantitative analysis of a copolymer using specular reflectance measurements obtained with the FT-IR microscope. In this analysis, the Kramers-Kroenig transformation was used to obtain extinction (k) values. The k values derived from specular reflection are quantitative agreement with absorbance values measured by transmission.
Automated FT-IR Grazing Angle Microscopy - A New Approach To Micro Spatial Chemical Mapping Of Thin Films
Frederick P. Eng
With the recent emergence of microscopes combined with FT-IR spectrometers, a new approach to micro-analyze polymer/organic materials has evolved. Samples with size and thickness less than 100 micrometers and 5 nm, respectively, can be analyzed. There are basically two types of infrared microscopes - near normal and grazing angle of incidence. The former provides both transmission and reflectance (near normal angle of incidence) sampling modes whereas the latter focuses only on reflectance using a grazing angle of incidence that ranges from 66 to 84 degrees. The grazing angle microscope, which relatively is more sensitive, is a better approach in analyzing or characterizing micro thin films, smears, or spots on reflective surfaces. Automation of the grazing angle microscope expands its capability further to study micro spatial chemical mapping of polymer, organic, and even inorganic thin films on reflective surfaces. The results yield the thickness map of the thin film in a micro-scopic scale that could not possibly or easily be archievedin the past by any analytical technique. Different mapping patterns such as straight lines, squares, rectangles, circles, spirals, sectors, and circular bands can be routinely accomplished using an IBM PC/AT that controls both the FT-IR spectrometer and the motorized X-Y and theta positioning stage of the microscope.
FT-IR Microscopy For Forensic Fiber Analysis: The Results Of Case Studies
Mary W. Tungol, Akbar Montaser, Edward G. Bartick
FT-IR microscopy is currently being evaluated as a routine technique for forensic fiber examination. All fibers matched by routine examination were also shown to match by IR data, however, further chemical characterization of the polymer was possible, thus increasing the evidential value of the fiber match. Several contaminants were identified and the utility of a fiber spectral library was tested.
FTIR-Microscopy Of Organic Microphases In Pharaonic Mummy Hair Samples
R. Kellner, Ch. Minich, N. Iskander, et al.
In this paper a unique application of FTIR-microscopy to problem solving in archeometry - the identification of preservatives in egyptian mummy hair samples from the 21st dynasty (1080 - 946 B.C.) is described. The precious samples were gently pressed into the surface of pure KBr-disks and the local distribution of dammar, tragacanth and myrrha determined. It was furthermore shown that the IR-microscopic approach gives very reliable data due to its relative freedom of contaminations as compared to extraction procedures.
Laser Transfer Of Organic Adsorbates: A Test Case Using Coronene Surface Patterns Transferred With Micrometer Resolution To IR Windows
M. DeVries, H Hunziker, H. R Wendt, et al.
It has been shown that molecules can be removed intact from surfaces by laser induced thermal desorption.(1) We show that this process can he used to transfer organic surface deposits across a vacuum gap to a transparent window such as NaCI for subsequent analysis by Fourier transform infrared spectrometry (PTIR). Experiments with thin film test patterns have revealed that a high degree of lateral resolution can be maintained in the transfer process. We attribute this to a strongly forward-peaked distribution of desorbed material. When the desorption wavelength is chosen such that the light is absorbed mainly by the substrate, a suitable power can be found to transfer all of the surface-deposited coronene to the transparent window. For example, rectangular spots of coronene can be transferred from a polished stainless steel surface, using 1.064 urn radiation, with no more than a 10 mrad spread of the pattern and with almost no loss of material.
Infrared Spectroscopy Of A Low Pressure Methane-Nitrous Oxide Flame
Kevin L. McNesby, Robert A. Fifer
A low pressure (<100 torr) CH4/N20 flame has been studied by FTIR spectroscopy. Qualitative species profiles were obtained as a function of height in the flame with a spatial resolution of 100μm. Temperature measurements over a 4 cm vertical range in the flame were done using the ro-vibrational line intensities of CO.
Quantitative Analysis Of Nitrocellulose And Pulp In Gunpowder By Using TGA/FT-IR
David J. Johnson, David A.C. Compton
Thermogravimetric Analysis (TGA) has routinely been used to quantitatively determine the presence of a specific component within a material by direct measurement from the weight loss profile. This technique works well when it is known that the detected weight loss was caused only by that component. If more than one material evolves during a single weight loss it is impossible to quantify the contribution of each individual component by using stand-alone TGA. However by coupling an FT-IR to the TGA one may assign evolved gases to a detected weight loss and potentially isolate each iny dividual material. Although a number of gases may evolve during one weight loss, the judicious selection of "Specific Gas Profiles" may allow the experimentalist to isolate each gas. The SGP is a measure of IR absorbance within specific frequency regions as a function of time. Through the use of standards, integration of theseprofiles allows the operator to quantitate the various components in an unknownp. Data from this research will show that nitrocellulose andpulp content in gun powder samples may be measured using the TGA/FT-IR technique.
Combined Rapid Ftir Spectroscopy And Thermoanalysis To Investigate The Kinetics Of Evaporation And Decomposition Of Liquids
H. H. Krause, N. Eisenreich, A. Pfeil
Evaporation and chemical decomposition are key processes in the combustion of liquids and liquid fuels. The parameters, however, which characterize these events are difficult to determine because the reaction intervals of evaporation and decomposition usually overlap. This overlap is of particular concern in the thermal analysis. By combining thermoanalytical and spectroscopic methods the desired parameters can be obtained in a straightforward manner.
Spectral Detection Of Magnetic Ordering: Diffuse Reflectance Of (Y1_xErx)2BaCu05
N. I. Agladze, G. G. Chepurko, E. P. Hlybov, et al.
This work demonstrates good possibilities offered by Fourier transform spectroscopy together with some special technique of diffuse reflectance in studying systems related to high-Tc superconductors. The spectra of green semiconducting phases (Y 1-xErx)2. BaCuO5 were measured and a magnetic order in these compounds at low temperatures has been established.
Double Modulation Techniques In Fourier Transform Infrared Photoluminescence
F. Fuchs, A. Lusson, J. Wagner, et al.
FT photoluminescence is a powerful tool to study mid infrared emission. However, problems may arise from thermal background radiation. A new phase locked modulation technique is presented and will be compared with existing double modulation (lock-in) techniques. The basic idea in our new technique is to apply a phase sensitive excitation of the luminescence instead of phase sensitive detection to separate the luminescence spectra from dominant thermal background radiation. As examples, luminescence of ZnS:Ni and Hgo.73Cdo.27Te are studied.
Dielectric Response Of InAs In The Far Infrared
A. K. Abdullah, T. J. Parker, C. Patel
The far infrared values of the real and imaginary parts of the complex dielectric response function of InAs below and above the reststrahlen band have been determined at approximately 300 and 100K. These quantities, i.e. E' and e", have been calculated precisely in terms of the optical constants n and k obtained using the method of dispersive Fourier transform spectroscopy1.
Chemical Modification Of Oxidized And Silicon Oxide Covered Aluminium Surfaces Studied By FTIR-MSR Spectroscopy
A. H.M. Sondag, M. C. Raas, F. J. Touwslager, et al.
Multiple Specular Reflectance (MSR) infrared reflection-absorption spectroscopy has been applied to study surface modification by organosilane (sub)monomolecular layers. The spectrum of octadecyldimethylmethoxysilane immobilized on an oxidized aluminium substrate is compared to the absorption spectra of the monomer and the disiloxane condensation product. Formation of hydroxyl groups on a Si02 covered aluminium substrate by a UV-ozon treatment is shown. Simultaneously, organic contaminants are removed from the surface by the UV-ozon treatment. The chemisorption of 3-methacryloxypropyldimethylethoxysilane on UV-ozon treated Si02 has been examined at different surface coverages. An increase of the number of organosilane species at the surface is accompanied by a decrease of surface hydroxyl groups.
Quantitative IR-Spectroscopy Of Interstitial Oxygen In Heavily Doped Silicon
A. Borghesi, M. Geddo, G Guizzetti, et al.
The interstitial oxygen content of heavily Sb-doped silicon wafers, up to 2 x 1018 at/cm3, has been measured by FTIR transmission, using a short baseline. The results of systematic measurements of two lots of 16 samples each, performed with FTIR and SIMS techniques, show a linear correlation between the two sets, although the IR technique estimates are consistently lower than those from SIMS.
Fourier Transform Infrared (FTIR) Determination Of Interstitial Oxygen Concentration Of Single-Side-Polished Silicon Wafers
Brian Rennex
This paper evaluates a new algorithm developed by the author for calculating interstitial oxygen concentration in silicon wafers, using infrared transmission data. These silicon wafers have an unpolished side and are referred to as being single-side-polished (SSP). This evaluation is carried out for various "unpolished" surface types, which are representative of etched or backside-damaged surfaces used by the integrated circuit industry. In general, accurate measurement of oxygen content is necessary for improvement of quality control in the manufacture of integrated circuits, and this quality control is more reliable and less costly if this measurement can be done on SSP wafers.
Study On The 1720cm-1 Absorption Band Of Cz-Si By Low-Temperature FT-IR Measurement
N. Nagai, Y. Nagasawa, H. Ishida, et al.
Temperature dependence of the so called 1720cm-1 band of Cz-Si has been studied. It has been shown, that temperature dependence of peak shift and height of the 1720cm-I band is similar to those of well known 9μm band. Temperature dependence of the half band width is almost the same as that of 9μm band above 100K. The present results indicate that the 1720cm-I band is a combination band of the 9μm band and a localized vibrational mode.
FT-IR Study And Intensity Calculation On The Hydration Of Acetonitrile
Liu Wentian, Weng Shifu, Wang Xiuzhen, et al.
During recent years, the FT-IR study on hydration of molecules attracted considerable interests. The peak positions and intensities of IR bands of some molecules change apparently after hydration. The theoretical explanation to these changes, especially to the intensity variation, is rather few. In this investigation, the effect of hydration on the IR intensity of acetonitrile has been systematically studied. Three parts are included: 1. Experiments: CH3CN-CC14-H20 systems were prepared from acetonitrile, tetrachloromethane and water. The volume percents of acetonitrile kept 80% in all solutions and the volumes of water in these solutions were 0.0, 3.0, 6.0, 9.0, 12.0 and 15.0% respectively. The infrared spectra of these solutions were measured quantitatively by Nicolet 7199B FT-IR spectrometer. It was found that the intensity of C-N stretching band(2200 cm-1) became stronger when water was added and the more the water was added, the larger the intensity increase was. This is caused by the formation of hydrogen bond between CH3CN and H20. 2. Normal coordinate analysis: The normal analysis of CH3CN was carried out. It was found that the IR spectrum of liquid acetonitrile could not be explained by the model of C3v symmetry of acetonitrile molecule. This effect on the IR bands is now under investigation. 3. The infrared intensity calculation: The atomic polar tensors (APT s) of CH3CN and CH3CN--H20 were calculated. The APIs of CH3CN were quite different from those of CH3CN--H20. The infrared intensities of C-N stretching bands in CH3CN and CH3CN--H20 were calculated respectively. The increase of IR intensity of C--N stretching band when water was added has been explained to some extent.
Evidence For The Presence Of A Distinct Phenol•Solvent Complex In Apolar Solvents From Numerical IR Bandsplitprocedures.
Bert Lutz, John van der Maas
The nature of interaction of a solute molecule with solvent molecules is interesting not only for a better understanding of physical phenomena but also from a biological point of view. In general the timescale of the infrared absorption process is faster than the lifetime of rotamers, conformations, aggregates and complexes. Therefore the FT-IR technique is suitable to study this type of interaction processes. Earlier the sensitivity of functional group vibrations to local intra- and intermolecular interactions has been reported for the OH-stretching mode [1,3]. We established that in non polar solvents like CC14 and CS2 both the frequency and the halfbandwidth reflect the solute-solvent interaction. Difference bandparameters derived from bandshape and bandmaximum in different non polar solvents (ΔHBW and vd) prove to be useful to characterize the type of hydroxylgroup and to quantify the degree of shielding. However, more insight was needed to explain frequency shifts and bandshape changes as result of solvent variation. Two general types of theories describe the solvent effect: (1) the interaction of one vibrating molecule within a solvent cavity and (2) the interaction of the oscillator with one solvent particle. Furthermore the influence of solvents on the infrared spectra has been correlated with refractive indices, dielectric constants, Taft parameters, van der Waals interactions and dispersion forces [2]. We have studied the OH mode of a phenol in mixtures of the apolar solvents CC14 and CS2 in order to disclose solute-solvent interaction. The bandshape in the mixture has clearly a composite character but does not show two maxima. Therefore bandsplitting based on "natural" bands has been applied to get insight into the separate components of the measured band for various ratios of CC14/CS2.
FT-IR Spectra Of The C=O And C-H Stretching Vibration Of Lauric Acid
Weng Shifu, Wu Jinguang, Xu Guangxian
FT-IR spectra of lauric acid in different media were examined. In very dilute solution of lauric acid in CC14, the two bands at 1711 and 1760 cm-1 the region 1650 to 1800 cm-1 were observed for the C=0 stretching modes of dimer and monomer of lauric acid, respectively. In n-butanol KBr pellet and fluorinated hydrocarbon media, the three bands at 1712, 1701 and 1687 cm-1 after deconvolution and curve analysis for the C=0 stretching mode can be observed. In the region of C-H stretching vibration, the wavenumber shifts of the CH2 symmetric and antisymmetric stretching bands of lauric acid in different media show that the packings of acyl chains of lauric acid in different media are not the same.
Conformational Analysis Of Starch Derivatives By FTIR Spectroscopy
Chris Bruijnes, Ron Bosman, Peter Bareman, et al.
Infrared spectroscopy appears to be a helpful tool for conformational analyses of starch derivatives. In this study spectral changes in the fingerprint region between 1200 and 900 cm-1 are related to changes in tertiary structures of P-cyclodextrin and linear dextrin inclusion complexes, linear dextrin after removal of complexed agent and amorphous amylose. The assumed similarity between the structures of β-cyclodextrin and linear dextrin inclusion complexes is confirmed by the spectra.
The Vibratr-Phonon Sidebands In The FTIR Spectra Of The Molecular Crystal CO2
H. W. Lowen, K. D. Bier, H. J. Jodl, et al.
FTIR investigations on polycrystalline CO2 at various temperatures show Stokes and anti-Stokes sidebands coupled to the vibrational modes v3, v2 and v+/v- (Fermi dyad). The latter is infrared forbidden and may be eliminated from spectra of good quality polycristalline films. The main peaks in the structure of the sidebands may be assigned to phonons from points of highest symmetry in the Brillouin zone. The vibron-phonon coupling process is mode specific and driven by electrical anharmonicity in case of v+ v- For the infrared allowed fundamentals, and especially at the Γpoint, the coupling process is also driven by mechanical anharmonicity. The dispersion of these internal modes at 1.0 influences the coupled phonons and thus the one phonon density of states is correctly mirrored by the v+ and v- sidebands only.
FT-IR Study On The Kinetics Of The Reaction Of 4,4'-Diisocyanatediphenylmethane With 1,4-Bdtanediol
Zhen Hua Xu, Zu Xiu Huang, Hong Jie Xu
The polyurethanes which have emerged as important industrial and biomedical engineering materials were synthesised by reaction of isocyanates with alcohols. Their reaction kinetics in the apolar solvents have been widely studied[1-3]. In the polar solvents which are really used in the practice synthesis, their reaction velocities are much higher than in the apolar solvents. Since the FT-IR spectroscopy has rapid and sensitive advantages, It has been applied to study the reaction of isocyanates in the formation of plastic foams [4], here we tried to study the reaction kinetics of 4,4'-diisocyanatediphenylmethane ( MDI ) with 1,4-butanediol (1,4-BD) in N,N-dimethylformamide(DMF) or dimethyl sulfoxide (DMS0) solvents utilizing this technique.
Electron-Donor-Acceptor (EDA) Complexes Of Aromatic Hydrocarbons With Organic Acceptors In Solution And In The Solid State. A Quantitative FT-IR Investigation.
Paolo Bruni, Elisabetta Giorgini, Giorgio Tosi, et al.
Liquid phase FT-IR investigation on π-π Electron-Donor-Acceptor (EDA) complexes between arenes and organic acceptors leads to values of formation constants that are in good agreement with the ones from other techniques (UV-Vis and NMR). In addition solid state FT-IR and UV-Vis determinations on the complexes are also reported and discussed.
FT-IR Spectroscopic Evidence Of Phase Transition For Naa-Roh-Kerosine-Hamicroemulsion System Containing NP Ions
Hua Liao, Zhenhua Xu, Nai Shi, et al.
In the previous investigation, the saponification of naphthenic acid extractant system has been proved to be a process of the formation of a microemulsion of 14/0 type, and its full extraction of rare earths is a process of destruction of the W/O microemulsion[1]. When NdCl3 is partially extracted with NaA (sodium naphthenate) secoctylalcohol-- kerosine-- water microemulsion system (ME), both the NdA3 and the NaA co-exist in the same organic phase. However,the formation mechanism of microemulsion containing neodymium has not been much studied. In this paper, 10 aliquots of fully saponificated extractants were equilibrated with various amounts of NdC13 solutions respectively, then ten organic phases with different extraction efficiencies of neodymium from 094 to 9094 were obtained. After extraction,the volume of neodymium containing organic phase increased by 5 to 4594, because of the transfer of water molecules. The appearance of these organic phase still remained clear and transparent. The average hydrodynamic radius of the drops were found to be 100-300 Angstrom by using light scattering techniques. The results give a direct evidence of the microemulsion formation in the organic phase. Their FT-IR spectra were measured with CaFa liquid cells utilizing a Nicolet 7199B FT-IR spectrometer. The presence of various amounts of water in the organic phases was clearly detected from the relative intensity changes of 1644 cm-I, which is assigned to the bending mode of 1110 molecules. Fig.1 shows the change of water contents to the percent extraction of neodymium. Comparsion with the FT-IR spectra, it is seen that the 1560 cm-1 peak of the full saponificated extractant is attributed to the asym. stretching vibration of COO′′′ group, it shifted to 1536 for 100% extration of Nd ions, indicating the formation of neodymium naphthenate (NdA ) from ionic sodium naphthenate. The sym. strethching vibration of COO′′′ located at 1406 cm-1, it shifted to 1408 cm in 45% Nd extration. and disappeared when the percentage extration of Nd3+ was larger than 50%, at the same time, the water content dropped sharply (Fig.1).These results suggested that a series of microemulsion containing Nd ions formed in these organic phases, at the transition region ( more than 50 percentage extration of neodymium), a morphological change of the W/0 dispersion system might occur.
Variable Temperature FT-IR Spectra Of Dicyclohexy1-18-Crown-16 Isomer C
Zhen Hua Xu, Hua Liao, Jin Guang Wu, et al.
The Dicyclohexy1-18-Crown-6CDC-18-C-6) is an important crown ether. In theory, there are five isomers -- A. B. C. D and E[1]. Recently, we have studied the variable temperature FT-IR spectra of isomer C and its complex with Er(NO3)3. Some interesting results which may concern conformation transfer were found.
A Comment To The Expansion Of Benzene Force Fields
Martin Ystenes
An extensive vibrational analysis of ethyl benzoate (EB) and its titanium tetrachloride complexes (1) has been performed. The phenyl force field was constructed by expanding a slightly modified Pulay-Fogorasi-Boggs benzene field (2) in three steps, through bromo-benzene, benzoic acid, and finally the ester (3). A good fit to the observed frequencies and splitting of the degenerate benzene vibrations was emphasized in all three steps.
Vibrational Study Of Poly(Ether Ether Ketone).
M. Dosiere
The medium infrared region (4000-400cm-1) has been widely used to study crystallinity because differences could be observed in the vibrational spectrum of several polymers which could be related to crystallinity as determined by X-ray diffraction, differential scanning calorimetry and density measurements. However, as crystallinity is concerned with packing of chains and interactions between neighboor chains, the absorption bands arising from such vibrations appear therefore at wavenumbers below 400 cm -1. Poly-(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene) or poly(aryl ether ether ketone) (PEEK),commercially introduced by ICI1, has been attracting increasing interest. It is a semicrystalline polymer with an unusual combination of properties such as high chemical resistance, excellent thermal stability as good mechanical properties. Taking into account of its high temperature high strength characteristics and melt processability, PEEK is generating interest for applications such as reinforced composites, coatings, electrical connectors, impeller housings... Fourier transform infrared spectroscopy is a quick and powerful tool to investigate orientation and/or crystallinity in polymeric materials.
Aqueous Infrared Spectroscopy - Potential Pitfalls Studies Of EDTA And Complexes In Solution
J. R. Powell, K. Krishnan
Due to the strong absorbance of water in the mid-infrared region of the spectrum, studies of aqueous solutions have usually been performed by either spectral subtraction of the pure solvent from the spectrum, or by substituting heavy water in the system to study absorbances below the 1640 cm-1 scissor. Both methods can lead to erroneous results, if invalid assumptions are made in each case.
Computer Simulations Of Depth Profiling By Photoacoustic Infrared Spectroscopy
Jonathan H. Perkins, Peter R. Griffiths
In photoacoustic (PA) spectrometry of solids, the sample is placed in a sealed cell in contact with a gas. Modulated radiation passes through the cell window and illuminates the sample. Absorbed radiation is converted to heat which is conductively transferred to the cell gas. The modulated heating of the gas produces pressure variations that are detected by a microphone, so that the signal is proportional to the sample absorptivity. As described by Rosencwaig and Gersho,1 the signal results from photons absorbed near the surface of the sample. The depth of this layer is called the thermal diffusion length, ps, and is determined by ps = (lc/ pC f ) 2 (1) where k is the thermal conductivity, p is the density, C is the heat capacity and f is the modulation frequency (Hz). For low-density polyethylene (LDPE), a modulation frequency of 10 Hz corresponds to a ps of 70 pm, and a frequency of 1000 Hz corresponds to a ps of 7 pm. This range of depths is appropriate for depth profiling of polymer laminates. One could imagine a PA depth profiling scheme where the laminate sample spectrum is measured at several modulation frequencies with spectral subtraction being applied to obtain the spectrum of each layer. One must include a valid scaling factor for spectral subtraction to yield meaningful results. Furthermore, the thermal diffusion length is not a distinct boundary, but rather is the inverse of the decay constant of an exponential attenuation function, A(x) A(x) = exp(-x/ps) (2) This function represents the attenuation of the heat from a modulated heat source at depth x reaching the surface of the sample and producing the signal. Because there is no simple solution that transforms the variation of PA signal with frequency to absorptivity versus depth, an iterative estimation approach was envisioned. In this iterative approach, a model laminate structure is guessed and the expected PA signal is estimated from a computer simulation. By iteratively adjusting and checking the model, one can derive an estimate of the laminate structure. In order for the iterative method to work, one must have a quick and accurate method for predicting the PA signal from a given laminate model. We have been investigating methods for doing these calculations.
Background Spectra For Rapid- Or Step-Scan FTIR Depth Profiling
R O Carter III, R. A. Palmer, R. M. Dittmar, et al.
The evaluation of a polymer of commercial significance to withstand processing and to perform properly has been generally a "trial by fire" process. As industry seeks to improve its product, control costs, and minimize environmental impact and waste, attention to system optimization and control are being pursued. To this end, the need to understand the chemical changes that accompany processing and/or weathering of polymeric systems is making new demands on analytical science. To meet these demands in a timely and direct fashion new techniques for obtaining spectro-chemical information are being investigated. One of these tools is the topic of this report, photoacoustic infrared spectroscopy (PAS-FTIR).
Design Considerations For Fourier Transform Spectrometry In The Near-Infrared And Visible Regions
Matthew J. Smith, Robert J. Rosenthal
Recent advances in the design of Fourier transform spectrometers have now made it possible to extend the spectral range of a single instrument from less than 50 cm-1 to greater than 30,000 cm-1. The most innovative of these instruments allow the sources, beamsplitters and detectors to be changed, and the instrument to be automatically realigned, all within a matter of seconds. As a result, it is possible to measure the electronic and vibrational absorption spectra of samples with the same instrument. In addition, with recent advances in the technique of FT-Raman spectroscopy using near-infrared and visible lasers, it is now possible to measure high resolution Raman spectra with the same interferometer as well. Thus, one Fourier transform instrument can serve to solve many molecular spectroscopy problems. However, extending the range of the interferometer to the shorter wavelengths of the near-infrared, visible and ultraviolet regions places critical demands on the quality of the optical system. To obtain a spectrum at high resolution at high energy, the interferometer moving mirror must travel absolutely perpendicular to the plane of the incident radiation. Any tilt in the moving mirror will degrade the optical resolution, with increasing severity at higher energies. In this presentation, some of the critical aspects of high resolution interferometry at short wavelengths will be discussed. The use of an ultra-stable Fourier transform spectrometer employing a dynamic tilt compensation mechanism will be shown for the measurement of spectra in the near-infrared and visible.
A Stationary Hadamard Transform Interferometer
J. D. Tate, Basil Curnutte, Robert M. Hammaker, et al.
Optical interferometers have been used extensively in many applied fields of science including chemistry and physics. Conventional interferometers have provided one, if not more of the following advantages over conventional dispersive spectrometers: (1) multiplex advantage (Fellgett's advantage) (2) high frequency precision (Connes' advantage) (3) high optical etendue' or throughput (Jacquinot advantage) There are many different types of optical interferometers available on the market today (e.g. Fizeau, Fabry-Perot, etc.,) but perhaps the most important, at least historically, is the Michelson interferometer. Most Fourier transform infrared spectrometers today are based on this design. The Michelson-type interferometer, which employs a beamsplitter and a moving mirror can be thought of as an amplitude splitting device. In other words, the original beam from the source is split in half by a beamspliiter with each half traversing one "arm" of the interferometer. One arm contains a movable mirror which modulates the interference fringe pattern generated as the two halves (i.e. each arm) are recombined by the beamsplitter. Since the movable mirror is translated with time, the interferogram is effectively recorded as a function of time. This temporal interferogram can be further related back to the optical path difference between the two arms of the interferometer. Stroke and Funkhouser proposed a Fourier transform spectrometer which created a spatial interferogram as opposed to the temporal interferogram produced by conventional Michelson-type interferometers. Some have referred to this device as a holographic spectrometer or source doubling interferometer. These devices can be thought of as wavefront splitting devices analogous to Young' double slit experiment or the Fresnel biprism. The primary source is split into two coherent secondary sources which will exhibit constructive and destructive interference in the plane. An appropiate Fourier transform of this interferogram will reconstruct the cosine frequency components of the primary source. There are many devices that make use of a spatial interferogram. Presently, in our laboratory, work is underway to develop a stationary Hadamard transform (HT) interferometer that utilizes a liquid crystal optical shutter array to encode a spatial interferogram created by a Fizeau interferometer design. Thus, the HT stationary interferometer becomes a no moving parts spectrometer.
Miniature FT-IR Spectrometer For Industrial On-Line Applications
Esko Herrala, Pentti Niemela, Tapio Hannula
There have been made some attempts to transfer the advantages of FT-IR to industrial use. Commercially available research grade instruments have traditionally been large and rather expensive. However, in many potential applications only medium resolution is required, especially when measuring liquid or solid samples. This means that the mirror displacement in a Michelson interferometer remains short and computation of the Fourier transform can be executed by a small computer. Medium resolution gives also other advantages in designing a spectrometer; simple source and detector optics, less severe requirements for mirror transport, and a small size.
A New Low Cost, High-Throughput Interface Card; Description & New Application Opportunities
Claude Lafond, Pierre Beauchesne, Frederick Baudais
The multiplex advantage of FT-IR spectrometers enables them to gather a full high quality infrared spectrum in a fraction of a second. However, the necessary transformation of raw interferograms to usable spectra is very computationally intensive. This Fourier transform step often greatly offsets the FT-IR speed advantage when performed on low cost microcomputer based systems. In order to reduce this calculation time to nearly zero compared with the computation time on an IBM AT TM, Bomem has developed the DSP100 signal processor.
Practical Aspects Of Forward And Reverse Energy Flow Spectroscopy Using The Bomem Da3 FT Spectrometer
H. Buijs, A. Zacharie
In modern materials analysis it becomes increasingly important to analyze samples at temperatures different from ambient using a variety of analysis techniques. The analysis techniques can be separated into various classes such as 1) transmission 2) direct absorption via photo conductive measurements or reverse energy flow from a warmer detector to a cooler sample 3) reflection at near normal incidence or grazing angle and 4) emission, with particular emphasis on induced emission such as photo luminescence and Raman scattering. The Bomem DA3 FT spectrometer is particularly convenient for the interfacing of a variety of cryostats and other large accessories to the standard, two sample beam, front sample compartment and the new, greatly enlarged, rear sample compartment, which has two sequential sample focus positions. The DA3 now offers a convenient way to switch between sources of radiation and detector modules at the so called input side of the spectrometer. This avoids the need for moving the sample and its accessory, such as a cryostat, between the output side and the input side (emission port) of the spectrometer: all measurement techniques may be performed with the sample and accessory in one position. Operational details and results of measurements will be presented.
Two-Dimensional Micro NIR FT Raman Spectroscopy
Bernhard Schrader, Andreas Hoffmann, Rolf Podschadlowski, et al.
Optical micro methods have an enormous potential of supplying analytical information: For every volume element complete spectra may be recorded. Since these techniques are non-destructive repeated analyses may be made even from precious samples. Micro techniques applying the methods of vibrational spectroscopy may supply detailed information concerning the composition of a sample, the identity and the structure of its components. The resolvable volume element is determined by the resolving power of the microscope and by the minimal amount of sample defined by the limit of detection. For Raman microscopes this is in the order of 1 cubic micrometer, for infrared microscopes in the order of 1000 cubic micrometers. Microscopes, however have an optical conductance) inferior to that of modern spectrometers. A compromise has to be found between the utilizable Raman light flux and spatial resolution. Both cannot be maximal under the same conditions. FT IR microscopes as well as Raman microscopes with dispersive spectrometers are supplied by several companies. The recently developed NIR FT Raman spectroscopy2 has the advantage of being essentially immune against fluorescence of impurities or products of decomposition.
Interferometer Measurements Of Stratospheric HCl From 1976 To 1985
H. Fast, W. F.J. Evans
Atmospheric absorption spectra obtained by means of balloon-borne BOMEM interferometers have been analyzed for trends in stratospheric gases. The interferograms were recorded, using the sun as the light source, on stratospheric balloon flights conducted by the Atmospheric Environment Service from 1976 to 1985. In this presentation the altitude distributions of hydrochloric acid derived from the near-infrared fundamental vibration-rotation band are reported. The R(1), R(2), and R(3) spectral lines of H35C1 at 2925.90 cm-1, 2944.91 cm-1, and 2963.29 cm-1, respectively, were used in the analysis. The results and the evidence for an increase in stratospheric HC1 are discussed in relation to other reported measurements and with respect to model calculations of stratospheric ozone depletion.
A Mobile FV-IR To Measure On-Site Emissions Of Volatile Organic Compounds (VOCS)
Martin L. Spartz, Jonathan H. Fateley, Mark R. Witkowski, et al.
A mobile laboratory for on-site analyses of volatile organic compounds (VOCs) using a FT-IR spectrometer is under development. Detection limits as an average concentration over a path length of 100 meters are estimated to be below 100 ppb. Preliminary field evaluation of the system capabilities is presently underway.
In Situ Measurement And Remote Sensing Of Gaseous Atmosphere
H. Rippel
The newly developed Double Pendulum Interferometer (DPI) with its unique optical design provides the possibility of remote and in situ measurements of exhaust gases in smoke-stacks. The remote configuration is presented in fig. 1. Due to its design the DPI guarantees for - high short and long term stability - insensitivity to external vibration and temperature changes (Ref. 1). The instrument not only identifies the type of gas but also allows a quantitative measurement of gas concentrations (Ref. 2). Fig. 2 gives the computed emission for a high temperature smoke-stack (HF, H20, CO2, and 02) for an in situ configuration. Reg. 1. Jaacks, R. G. and Rippel, H., Double Pendulum Michelson Interferometer with Extended Spectral Resolution, Appl. Opt., Vol. 27, 1988 2. Rippel, H., Quantitative Analysis Software for KT FTIR Instruments, Kayser-Threde, Technical Note, 1988
Design Tradeoffs For Air Monitoring By FT-IR
W. F. Herget, S. R. Lowry
As the price and detection limits of FT-IR instrumentation decrease the technique is receiving renewed interest as a method of measuring organic vapors in air. We will describe the results of several recent experiments we have performed in using FT-IR to monitor ambient air. We will also discuss several options that are available to make these measurements. As part of this paper we will report detection limits and how they apply to real world samples consisting of complex mixtures of organic materials.
Recent Advances In FTIR Photoacoustic Spectroscopy
John F. McClelland, Roger W. Jones, Jae Seung Oh, et al.
Advances in FTIR photoacoustic (PA) spectroscopy have significantly extended the scope and utility of the PA technique in the areas of: microparticle spectroscopy, compositional determinations via factor analysis, coal surface oxidation measurements, spectroscopy of highly opaque samples, and PA detector technology. A method is reported for measuring FTIR spectra of single particles in the tens of Am size range which uses a tungsten needle to pick up particles and hold them in the sample chamber of the PA detector. The tungsten needle is initially mounted on a micromanipulator and particle pick-up is performed under a microscope. The needle and sample are then transferred directly to the PA detector sample holder which positions the particle in the IR beam. No sample alignment or thinning are necessary. Compositional determinations of kaolinite and quartz in coal have been performed using the Perkin-Elmer CIRCOM factor analysis program. The IR spectra were collected by DRIFTS and PA methods using synthesized samples of known compositions for the learning set and unknown test samples. The PA spectra yielded slightly better correlations. Coal surface oxidation was studied using a calibrated UV irradiation of coal to generate carbonyl species, thereby gauging the freshness of coal surfaces by how much carbonyl is formed by the UV exposure. FT-IR-PA difference spectra are used to measure the increase in carbonyl. UV generated carbonyl is found to increase with surface freshness. This method avoids the need of a "fresh coal standard" which is difficult to reproduce. The method's probe depth is based on the decay length of UV rather than IR photons in coal resulting in an increase in surface specificity. The linearity of FT-IR-PA spectra as a function of absorbance has traditionally not been maintained at the peaks of strong bands in opaque samples. This leads to peak truncation and reduced spectral contrast. A method to extend linearity using the magnitude and phase information of the PA signal is reported based on the Rosencwaig-Gersho Theory of PA signal generations. Spectra of polymer slabs demonstrate the utility of this approach for enhancing spectral contrast. Developments are reported in PA detector technology which increase the scope of applications that commercial PA detectors can be used for. The new MTEC Photoacoustics Model 200 PA detector operates in diffuse reflectance, photoacoustic, and transmission measuring modes and handles both macro- and microsamples. The Model 200 has a simplified purging system and electronics designed for both fast scan and step scan FT-IR instruments. Spectra from a variety of applications are presented to demonstrate the Model 200 performance.
The Development Of Fourier Transform Infrared Ellipsometry.
O. Hunderi, J. Bremer, Kong Fanping
The feasibility of spectroscopic ellipsometry in the infrared spectral region has been investigated, and the first experimental results are presented. The actual configuration is based on a commercial Fourier transform spectrometer equipped with an ellipsometric attachment. The attachment is based on the socalled Beattie's ellipsometer and consists essentially of two wire grid polarizers and a mirror system of unit magnification. In order to ensure equal s- and p- components the polarization of the incoming beam is set 45° with respect to the plane of incidence. The measurements of the reflected beam are made at s-, s- + 45° and p- orientations of the analyzer. The system can thus be called a stepping analyzer, Fourier transform ellipsometer. In order to obtain maximum sensitivity the angle of incidence is close to the pseudo Brewster angle of the material to be studied. The complex dielectric function of the sample is obtained from observed data. Measurements are performed on doped and un-doped polymers (PEO, polypyrrole), semiconductors and liquid crystals (MBBA). This novel technique combines both the multiplex advantage of Fourier transform spectroscopy and the phase sensitivity of ellipsometry, and avoids the use of fast rotating components occurring in the conventional RAE mode.
A Super-Sensitive External Reflection Unit For FTIR Spectroscopy
Galen J. Hansen, Wilford N. Hansen
A new multiple external reflection unit for IR surface studies is described. The unit allows 14 or more reflections at near-grazing incidence, increasing the sensitivity over transmission by 78 and by 111 over a single reflection at 45°. Spectra of sub-monolayers on gold demonstrate the increased sensitivity.
Hadamard-Coded, Stationary-Entrance-Mask, Photodiode-Array Spectrometer
Roger A. Van Tassel, Wallace K. Wong
A Hadamard transform spectrometer has been designed which uses a stationary Hadamard mask at the entrance plane of a holographic grating, photodiode array spectrometer. The mask contains 2N-1 slots where N is the number of resolution elements in the photodiode array. The instrument uses no moving parts and has the ability to capture the spectrum of a randomly occurring pulse source with significantly higher signal-to-noise ratio than a single-slit array spectrometer. It utilizes all-reflective optics and is a generic design suitable for use in the ultraviolet, visible and infrared when equipped with a detector array which is sensitive in the region of interest.
Instrumental Needs For Hadamard Transform Spectrometry (HTS)
Jeffrey S. White, Robert M. Hammaker, William G. Fateley
Hadamard transform spectrometry utilizes a spatial transform, described by Hadamard mathematics,' in order to gain a multiplex advantage similar to that seen in Fouier transform techniques. A Hadamard instrument can be thought of to consist of five components: 1) optical separator (usually a grating), 2) Hadamard encoding mask, 3) post collection optics, 4) detector and 5) data processing (both hardware and software). Relevant qualities of each component will be discussed below. Limitations in the current encoding masks and possible alternatives are noted.
Optical Tolerances In Fourier Transform Spectroscopy.
J. R. Birch
A model is presented for the spectral degradation introduced into Fourier transform spectroscopy by imperfect optical figure. It allows tolerances to be defined for the figure of the optics if a required level of performance is to be achieved. It confirms the validity of the practical rule-of-thumb that optical figures true to within a tenth of the shortest wavelength of interest will not degrade performance unacceptably.
Fast-Scanning Fourier-Spectroradiometer BPS-01
A. A. .Balashov, V. A. Vaguine, G. N. Zhizhin, et al.
Fast-Scanning Fourier-Spectroradiometer BFS-01 was developed in Central Bureau for Unique Instrumentation of Academy of Sciences of the USSR for measuring spectral brightness of polarized electromagnetic radiation of high-temperature magnetized plasmas with high tempotal resolution in millimeter and submillimeter ranges. The instrument may be used to measure spectra from other non-stationary objects, say, for studying dynamics of transient physical and chemical processes. The spectral range of BFS-01 is from 2 to 100 cm-1 with the resolution 0.1 cm-1. The time needed to record one interferogram is 5 ms. The maximum number of interogramms (spectra) detected in one run as long as 200 ms is 20. The instrument consists of interferometer, power supply, vacuum system, radiation detector and optical commutator, which are designed as an integrated unit, and control system. The instrument and the local microprocessor controlled interfaces may be placed close to a physical facility to be studied while the personal computer may be removed to a se-parate room. The main part of the instrument is an interferometric layout (see Figure 1) in Martin-Paplette scheme allowing to detect simultaneously two interferogramms with orthogonal polarizations. The layout consists of two interferometers using one scanning device. At the input of each interferometer there are tungsten-wire grid polarizers. Beamsplitters and polarizers are also made of grids which are oriented in proper ways. Movable and immovable reflectors are dihedrons.
New FTIR Techniques For Studying Biological Membranes
Mark S. Braiman, K. Jeffry Wilson
Two new techniques useful for FTIR studies of biolog-ical membranes are discussed. First, we have developed a sensitive new method of obtaining attenuated total reflection (ATR) spectra of unilamellar lipid bilayers in con-tact with bulk water, by coating the bilayers on infrared-transmitting-optical fibers. Second, we have made several improvements in commercially available software for collecting time-resolved FTIR spectra; our modifications result in a substantial increase in data collection speed and a decrease in baseline artifacts in microsecond time-resolved FTIR spectra of biological samples.
Infrared Microtransmission And Microreflectance Of Biological Systems
S L Hill, K. Krishnan, J. R. Powell
The infrared microsampling technique has been successfully applied to a variety of biological systems. A microtomed tissue section may be prepared to permit both visual and infrared discrimination. Infrared structural information may be obtained for a single cell, and computer-enhanced images of tissue specimens may be calculated from spectral map data sets. An analysis of a tissue section anomaly may gg suest eitherprotein compositional differences or a localized concentration of foreign matterp. Opaque biological materials such as teeth, gallstones, and kidney stones may be analyzed by microreflectance spectroscop. Absorption anomalies due to specular dispersion are corrected with the Kraymers-Kronig transformation. Corrected microreflectance spectra may contribute to compositional analysis and correlate diseased-related spectral differences to visual specimen anomalies.
FT-IR Microscopy Of Biomineralization At 20µ Spatial Resolution
Richard Mendelsohn, Alborz Hassankhani, Nancy Pleshko, et al.
FT-IR microscopy offers certain advantages for the study of normal and pathological biomineralizing tissue samples. These include the identification and quantitation of the mineral phase and the determination of the secondary structure of the protein constituents. A drawback of the method is difficulty in interpretation of spectra from samples containing unknown quantities of unknown constituents. We have circumvented this problem by studying the main components of mineralizing tissue, collagen (95% of the protein phase) and hydroxyapatite (main mineral constituent) whose strongest IR bands absorb in relatively clean spectral regions. Samples were prepared for IR microscopy by surgical removal of tissue, fixation in formalin or ethanol, embedding in PMMA or epoxy, and the microtoming of thin (5-8μ) sections. Bulk embedding agent was mostly removed with methyl acetate. The sample was squeezed between BaF2 windows for IR studies. Any remaining PMMA or epoxy was removed by spectral subtraction. To evaluate the utility of FT-IR microscopy for study of biomineralization, two systems were examined:
Interaction Of Metal Ions With D-Glucose In Glassy State- -A Ft-IR Study
Ning Xi, Zhenhua Xu, Jinguang Wu
In recent years, it has become apparent that the ubiquitous carbohydrates of living matter perform a much broader biological role. This has stimulated the interest in examinations of the interactions between carbohydrates and metal ions. Some researches have shown that metal ions can coordinate to 0-1 and 0-2 hydroxyl groups of glucose and water molecules in cation/D-glucose complexes. The strong, sugar H-bonding network is rearranged upon D-glucose adduct-formation , and the a-anomeric configuration is favored by these metal ion coordinations1.In the present investigation, we have undertaken FT-IR spectral studies on cation/D-glucose samples in glassy state. A series of compounds including I A , II A , first row transition metal and lanthanide(Ln) chlorides were used to preapre the samples by the methods analogous to those of ref. 2. The IR spectra were recorded in the 4000-400cm-1 region with a Nicolet 7199B FT-IR spectrometer.
Composition And Coordination Of Non-Stoichiometric Calcium Bilirubinate'"
Zhanlan Yang, R . D. Soloway, Shifu Weng, et al.
Since calcium bilirubinate (CaBR) and its acid salt (CaHBR) were considered to be the main components of human pigment gallstone, these compounds were synthesized and investigated chemically, crystallographically and spectroscopically by several authors. In recent years, we found that the chemical compositions of these compounds varied from sample to sample, and the protonated carboxyl group of these samples was much more reactive than for bilirubin. It resembles the characteristics of human pigment gallstone. In order to enhance our understanding of the structure of gallstone, an investigation on the composition and coordination of calcium bilirubinate has been carried out. A series of CaHBR samples were prepared by reacting diluted pyridine solutions of bilirubin and
How Metal Ions Affect The Infrared Spectra Of Poly A And Poly U
Bao-Zhu Yu, Wilford N. Hansen, Jin-Guang Wu, et al.
The FTIR spectra of Poly A and Poly U with metal ions as Li+, Na+, K+, Ca++ indicate that the C-N, C=C, C=0 and NH2 group in adenine and uracil base and the -P02 group are the active sites in the interaction between metal ions and nucleic acids.
FT-IR Spectroscopy As A Tool For The Study Of Metal Ions/D- Galactose Complexes
Ning Xi, Shifu Weng, Jinguang Wu, et al.
Complex-formation of carbohydrates with metal ions has been implicated in a variety of biological process. We are currently investigating the FT-IR spectra of the mixtures of metal ions and carbo-hydrates to elucidate the structural factors involved in these samplesl. In this paper, we described the FT-IR spectral evidence of the formation of CaCl2 ZnCl2 and NdC13/D-galactose complexes in glassy state.
FT-IR Study On The Hydration Of Calcium Bilirubinates
H Guo, R. D. Soloway, Z Yang, et al.
Comparison of the dessicated and hydrated forms of the neutral salt of calcium bilirubinate indicated that water alters both the C-E1 skeleton and the polar groups of the molecule, suggesting that water may considerably alters the conformation and, therefore, the properties of calcium bilirubinate. The small degree of swelling indicates that some cross-linking is present in this ionic polymer but that it is much less than in whole pigment gallstones, suggesting that other molecules, possibly glycoproteins, provide much of the cross-linking.
FTIR Examination Of Thermal Denaturation And Gel-Formation In Whey Proteins
D. Michael Byler, James M. Purcell
Second derivative Fourier-transform infrared [DR2-FTIR] spectra of β-lactoglobulin [RIG], serum albumin [BSA], and a-lactalbumin [aLA], three proteins found in bovine whey, are markedly different before and after thermal denaturation. In no case, however, do the heat-treated proteins unfold as completely as does alkaline-denatured RLG [1]. The spectra also suggest that, for RLG and BSA, formation of intermolecularly hydrogen-bonded (β-strands precedes the onset of heat-induced gelation.
The Binding Effect Of Metal On The Secondary Structure Of Albumin
Ly Li, Wentian Liu, Jinguang Wu, et al.
On the basis of vibrational analysis, the deconvolution and derivative procedures of amide bands in IR spectra has stimulated the interests in the study on the secondary structure of protein [1, 2]. The inter-relationships between metal ions and binding substances such as protein are important in the living system. However, the influnce of metal ions on the secondary stucture of protein has not been studied in details by this technique. In this investigation, NaC1, KC1,ZnC12, MgC12, CaC12, AlC13, NaNO3, AI (NO3)3, PrC13,NdC13,EuC13,DyC13, TbBr3, Ce(NO3)3, andGd(NO3)3 were reacted with bovine albumin in aqueons solutions for 4-5 hours respectively. The albumin complexes were formed both in supernatants and precipitates. Their FTIR spectra were measured with BaF2 pellet for the precipitates and cast film on BaF2 windows for the supernatants, utilizing a Nicolet 7199B spectrometer.
Sampling And Resolution Enhancement Techniques For The Infrared Analysis Of Adsorbed Proteins.
M. P. Fuller, B. R. Singh
In this report, we have analyzed the secondary structures of the dichain form of tetanus neurotoxin using. FT-IR and circular dichroic spectroscopies for a-helix, β-sheets, β-turns and random coils. These results indicate that the secondary structures are significantly different from those reported in earlier studies in that it shows much higher content of ordered structures (~50%) which could be significant for the function of the neurotoxin.
Optimization Of A Window Fourier Domain Search System
Jeffrey W. Sherman, James A. de Haseth
Several methods are presented for optimizing the quality of results returned from a window Fourier domain search system. These techniques include choosing the best spectral range, smoothing, baseline correction, and calibration of data using interpolation. While window Fourier domain search systems perform quite well, minor adjustments to the spectral domain data improve the quality of results significantly. These improvements are particularly important in cases where the data are extremely similar, such as spectra of compounds in a homologous series.
Partial Least-Squares Calibration Diagnostics Applied To The FT-IR Analysis Of Borophosphosilicate Glass (BPSG) Thin Films
David M. Haaland
Full-spectrum multivariate calibration methods are capable of providing a multitude of diagnostic capabilities for evaluating the quality of the calibration, identifying problem calibration samples, and flagging unknown samples whose analysis by these methods might be unreliable. These diagnostics are demonstrated for the analysis of BPSG thin films on silicon using infrared spectroscopy and partial least-squares methods.
Quantitative Analysis Of Spectral Data By Combined Deconvolution And Curve-Fitting
Richard S. Jackson, Peter R. Griffiths, John A. Pierce, et al.
Curve-fitting (CF) and deconvolution are both established techniques for obtaining quantitative information from complex spectra, but they both have limitations. If CF is to be applied to heavily overlapped bands it is often impossible to determine the number of component bands present, and the band parameters obtained can be subject to large errors. The main disadvantage of deconvolution is that the choice of the parameters is often very subjective, and if incorrect can lead to erroneous results. In this work the advantages of combining the two techniques are investigated, and it is demonstrated that the problems outline above can be largely overcome. A comparison is made in this context of the relative merits of two methods of deconvolution: Fourier self deconvolution and maximum likelyhood restoration.
Quantitative FTIR Analysis Using Aultivariate Techniques
R. P. Durnan, D. J. Wood
A caparison of the quantitative analysis of simple alcohol/ether sixtures using Principal Component Regression and Partial Least Squares analysis is reported and shows the latter method is lore suitable for analysis.
Precision In Infrared Quantitative Analysis; Absortance Is The Key
H. A. Willis, N. Sheppard, J. Chalmers
Quantitative analysis in the infrared region is normally made through the experimental measurement of absorbance, A, which is related by the Beer-Lambert Law to concentration by the equation
On-Line Analysis Of Fermentation Of Dairy Waste
P. Fairbrother, W. O. George, J. M. Williams
A fermenter was constructed in which cheese whey was converted into ethanol by the yeast Candida pseudotropicalis ATCC 8619. The reaction mixture was continuously circulated through an internal reflection flow-through cell located in the cell compartment of an FT-IR spectrometer. Methods were developed to analyse the substrate (lactose) and product (ethanol) continuously. The results provided information on the conditions necessary to optimise a potentially important process.
Comparison Of Multivariate Calibration With PCR And PLS For Glucose Using Infrared Spectra Of Human Whole Blood
R. Marbach, H. M. Heise
The calibration of glucose in whole EDTA blood was carried out using FT-IR spectra obtained with a micro-CIRCLE cell in the range of 1500 - 750 cm-1. The reference concentrations had been measured by the enzymatic glucose dehydrogenase method. The P-matrix approach was chosen applying the Partial-least-squares (PLS) and Principal component regression (PCR) algorithms. The optimum model for predictipns was obtained by PLS achieving an average prediction error of 19.8 mg/dL based on PRESS1 from crossvalidation. The calibration results for both algorithms are discussed. PLS is favoured on the grounds of numerical and statistical advantages.
Intensity Corrections For Gas Temperature Determinations At High Temperatures From FTIR Absorption And Emission Measurements
Robert A. Fifer, Kevin L. McNesby
We are investigating species and temperature profiles in low-pressure pre-mixed flames using FTIR spectroscopy. As part of this project, we are seeking reliable methods of obtaining rotational temperatures. Because it is a common participant in most combustion reactions, we have chosen carbon monoxide for the initial st0;ies. Our calculational methods are extentions of the work of Anderson and Griffiths'' (for CO at T < 150°C (423°K)); to test our methods, we have measured CO absorption spectra from 40 to 600°C, and emission spectra from 100 to 600°C. Obtaining the rotational temperature of CO at high temperature (>423°K) from the structure of the v=0 - v=1 ro-vibrational band is complicated by three factors: The first and most important factor is the distortion of true peak intensities by the spectrometer resolution due to convolution of the spectrometer lineshape function and the true line profile. For absorption of a collisionally-broadened line convolved with an instrument lineshape gunction resulting from triangular apodization, the recorded transmittance is given by:.) T1 = I exp{-2.303 A pmam2/((v-vm) 2+a2m)}Dsin2(πD(v-v1))/(πD(v-v.))2 dv (1) where T1 = transmittance of line m when the instrument is set at frequency i, am = half width of half height of line m, vm = frequency at center of line m, v = frequency at which instrument is set (or reporting), D = slit width or optical retardation, and Apm = true peak absorbance of line m at vm . The second complicating factor is overlap of some lines with weak lines due to 13C16O;; this factor was taken into account by Anderson and Griffiths. The third factor which complicates temperature calculations is that some of, the lines in the v=0 - v=1 band of CO overlap with lines from the v=1 - v=2 transition.4 Figure 1 shows a portion of the CO absorption spectrum using 0.125 cm-1 resolution Visible in this spectrum are both "hot band" transitions as well as those due to 13C160. Because the "hot bands" are much stronger at high temperature (>300 or 400°C) and become more important as temperature increases than those bands due to 13C16O, we have decided to initially ignore l3CI160 bands. Figure 2 shows linecenter separation between "normal" and hot bands as a function of frequency for CO.
Infrared Emission Spectroscopy
Milan Milosevic
This paper gives the complete theoretical description of emission spectroscopy. The approach, based on Einstein's derivation of the emission of a perfect black body, has been adopted. The strict general result has been obtained. An approximate result from the emittance of real samples is derived and applied to the the case of a thin film and an optically opaque sample. Theoretical results have been illustrated by a realistic numerical simulation.
Transient Infrared Emission Spectroscopy
Roger W. Jones, John F. McClelland
Transient Infrared Emission Spectroscopy (TIRES) is a new technique that reduces the occurrence of self-absorption in optically thick solid samples so that analytically useful emission spectra may be observed. Conventional emission spectroscopy, in which the sample is held at an elevated, uniform temperature, is practical only for optically thin samples. In thick samples the emission from deep layers of the material is partially absorbed by overlying layers.1 This self-absorption results in emission spectra from most optically thick samples that closely resemble black-body spectra. The characteristic discrete emission bands are severely truncated and altered in shape. TIRES bypasses this difficulty by using a laser to heat only an optically thin surface layer. The increased temperature of the layer is transient since the layer will rapidly cool and thicken by thermal diffusion; hence the emission collection must be correlated with the laser heating. TIRES may be done with both pulsed and cw lasers.2,3 When a pulsed laser is used, the spectrometer sampling must be synchronized with the laser pulsing so that only emission during and immediately after each laser pulse is observed.3 If a cw laser is used, the sample must move rapidly through the beam. The hot, transient layer is then in the beam track on the sample at and immediately behind the beam position, so the spectrometer field of view must be limited to this region near the beam position.2 How much self-absorption the observed emission suffers depends on how thick the heated layer has grown by thermal diffusion when the spectrometer samples the emission. Use of a pulsed laser synchronized with the spectrometer sampling readily permits reduction of the time available for heat diffusion to about 100 acs .3 When a cw laser is used, the heat-diffusion time is controlled by how small the spectrometer field of view is and by how rapidly the sample moves past within this field. Both a very small field of view and a very high sample speed would be required to attain a diffusion time of 100 μs. Accordingly, pulsed-laser TIRES generally produces spectra suffering from less self-absorption than cw-laser TIRES does, but the cw-laser technique is technically much simpler since no synchronization is required.
Fourier Transform Spectroscopy Of Free Radicals: BC, CCN And CH3N
W. T.M.L. Fernando, C. Brazier, N. Oliphant, et al.
The visible and ultraviolet emission spectra of the BC, CCN and CH3N free radicals were recorded in emission with the Fourier transform spectrometer associated with the National Solar Observatory at Kitt Peak. The Fourier transform spectrometer is a powerful tool for the identification of weak spectra of free radicals.
Use Of A GC/IR System As A Variable Temperature Gas Cell
G. Jalsovszky, J. Varga
A GC/IR system with no stopped-flow facility has been used to take gas phase spectra of good quality. Concentration in the light pipe can be controlled, enabling one to measure absorption coefficients as illustrated on the example of benzene and ethanol.
The Use Of Headspace GC/FT-IR For The Monitoring Of Volatiles In Commercial Brand Coffees
Senja V. Compton, David A.C. Compton
Recently, the area of food analysis and product safety has become of major concern to consumers. Therefore, companies involved in the quality assurance of theirproducts have been encouraged to perform extensive analyses to guarantee safety and satisfaction. One of the largest consumer products in the beverage marketplace is coffee. Much emphasis has been placed upon the safety of the decaffeination processes used by various manufacturers; these involve extraction of the caffeine by a solvent system that may be aqueous or organic, and is sometimes,super-critical. Additionally, aroma (fragrance) of brewing coffee has been found to be of major concern to the individual by the marketing departments of the coffee companies. The heads ace analysis of coffees can be used to discover the species retained after the decaffeination of coffee, as well as to distinguish the volatile species released upon treatment of the coffee at boiling water temperatures.
The Optical Design And Application Of Light Pipe systems In FTIR Spectrometer
Ming Yin, Bao-Zhu Yu, Wilford N. Hansen
The light pipe is a very useful tool to study infrared spectra of powders and layers. Three optical systems using light pipes will be discussed.
Detection Parameters In Magic-LC/FT-IR
Glenda K. Ferguson, James A. de Haseth
Detection limits using the Monodisperse Aerosol Generation Interface Combining Liquid Chromatography with Fourier transform infrared (MAGIC-LC/FT-IR) spectrometry have been studied. Caffeine and p-nitroaniline samples were deposited from both water and 50:50 methanol:water solutions. Various quantities of solutes were injected and deposited on KBr windows. Infrared spectra were taken and compared with reference spectra obtained from the deposition of a relatively concentrated solution.
Advantages And Disadvantages Of A Chromatographic/FT-IR Interface Based On Mobile Phase Elimination
Kelly L. Norton, Andrew M. Haefner, Hideo Makishima, et al.
Interfaces between chromatographs and FT-IR spectrometers based on mobile phase elimination and eluite deposition are usually more sensitive than flow cell methods. In the GC/FT-IR 1,2 and SFC/FT-IR314 interfaces developed by our group, the eluites are deposited in a small area (<0.04 mm2) on a moving infrared transparent window (usually ZnSe) and their spectra are measured using an FT-IR microscope. One advantage that has been ascribed to this technique is the ability to use standard condensed phase spectral libraries for spectral searching.5 In this paper, the results of a systematic study are described in which SFC/FT-IR spectra are compared to libraries of condensed phase reference spectra. The particular analytes that were investigated were chosen to probe several possible sources of variation between SFC/FT-IR spectra and reference spectra of the same compounds prepared as KBr disks.
Infrared Spectroscopic Determination Of Low Temperature Phase Transitions In Crystals (Organic Compounds)
S O Paul, C J H Schutte
The changes occurring in the infrared spectra of 5,8-dihyroxy-1,4-naphthoquinone (naphthazarin) and 1,2,4,5-tetrachlorobenzene when the temperature is lowered from 298 K to 4 K have been examined. The phase transition which occurs in naphthazarin can be determined, because some vibrations are affected by the transition.
FTIR And Raman Studies On Solid Nitrogen Dioxide: Temperature Cycling Of Ordered, Disordered And Multicomponent Layers.
A. Loewenschuss, A. Givan
FTIR spectra of nitrogen dioxide layers deposited at various rates and substrate temperatures, are reported. Bands assignable to N2O4(D2h) (ordered and disordered layers), to 0=N-O-NO2 "D" and "D'" isomers, to NO+NO3- nitrosonium nitrate and to the NO2 monomer were observed. The relative amounts of species depends upon deposition conditions. Temperature cycling effects were followed up to 205 K.
A Variable Temperature FT-IR Study Of The Liquid Crystalline Behaviour Of Octakis(N-Hexoxy)Phthalocyanine-Copper(II).
Bert Lutz, John van der Maas, Johan van der Pol, et al.
Phthalocyanines (Pc) have unique physical properties which make them interesting for different fields of application. The mobile n-electrons within the Pc-nucleus provide the basis for their semiconducting behaviour. Extension of the electrical conductivity is being pursued by increasing the π-πoverlap between several Pc units. The liquid crystalline behaviour of extended stacks of disc-like peripherally substituted octa-n-alkoxy Pc's has been reported earlier [1]. X-ray powder diffraction studies showed a stacked hexagonally arranged ordered columnar structure (Dho) for the mesophase (Fig. 1). The ability to trace small changes in the absorption bands makes FT-IR ideally suitable for the study of conformational changes and intermolecular rearrangements. It has been shown that not only the bandmaxima but also the integrated intensity and bandwidth are sensitive to phase transitions [2,3,4,5].
Variable Temperature Ftir Spectroscopy Of Transition Metal Complexes Using The Scn Reporter Ligand.
Rolfe H . Herber
Due to its large oscillator strength, as well as its position in the IR spectrum (ca. 2100 cm-1) which is relatively free of interferences, the CN stretch absorption in transition metal thiocyanate and iso-thiocyanate complexes has long been used as a diagnostic measure of both the ligand binding mode, as well as an indication of molecular point-group symmetry. In bis-SCN complexes of the first-row transition metals having (distorted) D, symmetry, cis complexes are expected to show two absorbances, corresponding to the sym and asym stretching modes, while for trans complexes (D,) having inversion symmetry, the sym stretch should be IR forbidden and Raman allowed, while the asym stretch is IR allowed and Raman forbidden. Similar considerations apply to square planar complexes (Cav and D). In this study, a number of octahedral and square planar transition metal bis-thiocyanate (isothiocyanate) complexes of Mn(II), Fe(II), Co(II), Ni(II),Cu(II), Ru(II) and Pt(II) have been synthesized, and characterized. by variable temperature IR spectroscopy both in KBr and Kel-F grease mull matrices. Depending on the steric requirements of the other ligands, the characteristic signature of the pseudohalide stretching mode is found to depend critically on the (near) degeneracy of the sym and asym CN stretching modes. Low temperature IR data, as well as supporting nmr and Raman spectroscopic results are required to completely characterize the geometry of these inorganic and metal organic complexes.
In-Situ Monitoring Of Amine-Isocyanate Reaction By Internal Reflection FTIR
Darlene M. Back, Paul Buscemi, David Palmer
The solution-phase reaction of a diaminopyridine and diisocyanate has been studied in-situ using a cylindrical internal reflection cell as the reaction vessel. The spectra obtained as a function of time and the plots of the intensity of the corresponding reactant and product absorption bands are discussed.
Diffuse Reflectance FT-IR Of Surface Modified Kevlar
R. Benrashid, G . Tesoro, M. T. McKenzie, Jr.
Diffuse reflectance FT-IR (DRIFT) has been applied to the characterization of surface modified Kevlar 29 and 49 fibers. The surface modifications include amination and sulfonation. The standard DRIFT experiment has been modified in the manner first described by Koenig et.al. 1 who used a KBR overlayer to enhance surface functional IR bands. The results from the DRIFT experiment have been correlated with those from a standard dye test. The results for degree of modification are in reasonable agreement between the two measurement approaches. However, the dye experiment is time-consuming and inconvenient. DRIFT has been shown to be useful in characterizing modified Kevlar surfaces in as-used conditions.
FT-IR Study Of Chemical Changes, Occuring During Co-Extrusion Pulverization Of Ldpe With Styrene-Butadiene Rubber
Leonid V. Vladimirov
The chemical structure changes in polymers under conditions of molding, extrusion, or other fabrication techniques can be important factors affecting the macroscopic properties and applications of the resulting materials.
Sapphire Fibers As In-Situ MIR Cells For Monitoring Reactions Of Polymers
Mark A. Druy, Lucy Elandjian, William A. "Chuck" Stevenson, et al.
The feasibility of using an embedded optical fiber as in-situ sensor to transmit infrared radiation was demonstrated. The cure of a graphite fiber/epoxy matrix was effectively followed by noting the behavior of characteristic infrared absorptions.
Structure Of Skin And Core In Polymer Films
Giuseppe Zerbi, Germana Gallino
The relative amount of amorphous (confomationally irregular)and crystalline material is an experimental quantity relevant in basic and applied polymer science. Normally infrared transmission spectroscopy is routinely used for both qualitative and quantitative studies in this field.
Fiber Optic FT-IR Spectrometry Of Laminates
Jennifer E. Andrews, James A de Haseth
The process of lamination can be monitored by the use of fiber optics coupled with Fourier transform infrared (FT-IR) spectrometry. During the process, the effects of temperature and pressure on the laminate and fiber can be followed. Problems related to the temperature, stripping, and pressure on the fiber have been addressed. Temperature has virtually no effect on the fiber up to about 350°F. Stripping the fiber using the manufacturer's recommended method was detrimental to the surface of the fiber. Pressure (up to about 400 psi) on the fiber was not a problem unless the coating of the fiber was removed by the prescribed method.
Sample Depth Profiling By Pas/Step-Scanning Interferometry: Consideration Of Mirror Positioning Errors
Bruce Lerner, Jonathan H. Perkins, Gilbert L. Pariente, et al.
Although step-scanning interferometers were developed concurrently with rapid-scanning interferomters, the latter dominates the commercial market. However, recently there has been a resurgence of interest in step-scanning interferometers as demonstrated by the recent publications 1,2 and the introduction of a commercial system by Bruker with a step-scanning option. Using a step-scanning interferometer is particularly advantageous when photoacoustic spectroscopy (PAS) is being performed. PAS has the ability to depth-profile a sample. This can be accomplished by varying the modulation frequency of the impinging radiation, which varies the penetration depth (more properly known as the thermal diffusion length, μs) by the equation:5 μs = (k/ πρCf)0.5 where k is the thermal conductivity, ρ is the density of the sample, C is the specific heat of the sample, and f is the modulation frequency of the radiation. In a rapid-scanning Michelson interferomter, the modulation frequency is equal to 2Vv Hz,6 where V is the optical velocity and v is the wavenumber. Since V is a constant, the modulation frequency is proportional to the wavenumber of the incident radiation. Thus, the penetration depth will vary across a spectrum. A step-scanning interferometer alleviates this limitation. Radiation modulation in a step-scanning interferometer is accomplished by either an external chopper (amplitude modulation) or by vibrating an interferometer mirror (phase modulation) and thus all of the radiation is modulation at the same frequency. Thus, penetration depth is uniform across a spectrum. The ability of the step-scanning interferometer/PAS combination to depth profile is demonstrated in this work. No consideration has ever been given to the effect of mirror positioning inaccuracies on the signal-to-noise ratio in PAS measurements. The interferogram is collected by stopping the moving mirror once every laser wavelength at the mid-points of the laser interference record. By analogy to a rapid scanning interferometer, these are known as the Laser Zero Crossings (LZC). The maximum signal-to-noise ratio allowed for by a positional error t is given by:3 SNR = (4/Ai5max) where 'max is the maximum spectral wavenumber. Positioning inaccuracies can be from the failure of the mirror to be moved between equally spaced intervals of retardation or from the effect of mirror drift once at these sampling points. The instrument used in the present study utilizes a mechanical drive that was observed to drift more than 10 nm from the desired retardation position over a period of a few seconds. To correct for this drift a piezoelectric transducer (PZT) was mounted between the drive and mirror; this is discussed more fully and the ability of the PZT to maintain the mirror position is demonstrated.
Accurate Determination Of The Spin-Orbit Splitting Of The Valence Bands Of Silicon By Means Of Fourier Transform Photothermal Ionization Spectroscopy (FT-PTIS)
S. C. Shen, Zhiyi Yu, Y. X. Huang
By use of the FT-PTIS technique, the transitions from the ground state of boron to its excited states associated with the p3/2 valence band as well as to those associated with the p1/2 valence band have been observed for ultrapure silicon. According to the positions of 2p', 3p' and 4p' lines, and considering the nonparabolicity of the P1/2 band, the ionization energy of boron to the p1/2 band was deduced as EI(boron) = 88.45± 0.01 meV with high accuracy and without doping broadening of the line width. From the ionization energy of boron to the P3/2 band determined as E1(boron) = 45.83 ± 0.01 meV, the spin-orbit splitting of the valence bands in silicon has been determined to be Δo(Si) = 42.62 ± 0.01 meV, which seems to be the most accurate one so far.
Negative Light Flux Spectroscopy Of High-Tc Superconductors
N. Yu . Boldyrev, V. M. Burlakov, G. N. Zhizhin, et al.
The results of negative light flux spectroscopy of the supposed energy gap region of oriented films and the phonon spectra of bulk polycrystalline materials of high-Tc superconductors will be discussed in this presentation.
Infrared Fourier Transform Spectroscopy On Local Vibrational Modes In GaAs
B. Dischler, H. Seelewind, W. Jantz, et al.
Fourier transform infrared (FTIR) spectroscopy has been used to measure local vibrational mode (LVM) absorption from impurities in GaAs. Carbon on an arsenic site (CΑs) is a typical residual shallow acceptor in undoped semi-insulating GaAs and the exact determination of the carbon concentration by LVM spectroscopy is of technical importance. The calibration factor by which the integrated LVM absorption is converted into carbon concentration has been found to depend on sample temperature and on instrument resolution [1-3]. For a 0.3 cm thick undoped GaAs sample with 2x1016 cm-3 carbon we measured the LVM band at temperatures between 5 and 300 K with a resolution of 0.1 cm-1 (Fig.1). At low temperatures the CΑs LVM band splits into five individual lines [4] due to different isotopes among the four Ga ligands (60.4% 69Ga, 39.6% 71Ga). We have plotted the temperature dependence of the center frequency (Fig 2a), of the width of the individual lines (Fig 2b) and of the integrated absorption area (Fig 2c). Remarkable is the similarity of the frequency variation with the lattice expansion [5] in Fig. 2a and the 30% decrease in oscillator strength above 150 K in Fig 2c.
FTIR External Reflection Study Of Molecular Orientation On Semiconductors
Jerzy Mielczarski
An infrared external reflection technique has been developed to study the structure of spontaneously adsorbed layers of surfactants on semiconductor (cuprous sulfide) from aqueous solution. Owing to the optical properties of the substrate, positive as well as negative absorption bands are observed in the spectrum depending on the angle of incidence and the polarization. Knowledge of the three theoretically calculated absorbance components, AIIX, A2z and Aiy, makes it possible to predict the absorbance values which match with experimental data and provides for an easier interpretation of the reflection spectra, especially for the case of an anisotropic layer. Generally good agreement has been obtained between experimental and calculated absorbance values.
The Characterization Of Organic-Charge Transfer Superconductors By Microreflectance Spectroscopy
J. R. Ferraro, S. L. Hill, K. Krishnan
Certain classes of organic charge-transfer salts demonstrate superconducting behavior at liquid helium temperatures. Single crystal x-ray diffraction and microreflectance FT-IR analysis have been performed on several conductin systems to deduce the nature of the crystalline structure which affect theg electrical conductivity. The infrared spectrum for a single crystal salt exhibits absorptions from the unsaturated organic salt as well as influences from the electronic transitions. There are strop correlations between particular absorption profiles and the single crystal conductivity. Routine examination of the long-term stability of the morphology as well as contamination of the single crystal may be studied.
A Comparison Of Multicomponent Quantitative Analysis Methods For The Determination Of Boron And Phosphorous In Bpsg Films On Silicon
P. J. Stout, K. Krishnan
Borophosphosilicate glass (BPSG) films are frequently used in silicon integrated circuits for multilevel interconnection coatings and for surface passivation to provide mechanical protection and improve electrical stability and reliability. BPSG films also act as "getters" of sodium and other metal ions impurities which might otherwise drift to the oxide/silicon interface and affect the electrical properties of the device. Many of these applications require careful control of the phosphorous and boron concentration in the glass film; consequently a rapid and precise measurement of these components is needed. Infrared analysis of BPSG films provides one non-destructive method for the determination of boron and phosphorous in BPSG films deposited on silicon. The BPSG analysis is done from the transmission spectra of silicon wafers coated with the BPSG film. Since heavily doped silicon exhibits continuous plasma absorption in the region where BPSG bands are present, the BPSG film should be deposited on silicon substrates having a resistivity of greater than 10 ohm-cm. A typical transmission spectrum of a BPSG film deposited on silicon is shown in Fig. 1. The phosphorous in the film is normally detected by measuring the band centered at about 1335 cm-1 which arises from P-0 stretch in the P205 moeity in the film, and the boron is measured from the B-0 stretch band centered at about 1420 cm-1. This absorption is from the B203 moiety. Normally, when BPSG glass films are deposited on the silicon substrate, the deposited films contain the phosphorous in different chemical forms - P2O5, P203, etc. - and also contain some trapped hydroxyl groups or moisture. The moisture may react with the P205 to form phosphoric acid. When this happens, and there is some P203 present in the film, the infrared methodology may not detect all of the phosphorous in the film since only the 1335 cm-1 band due to P2O5 is observed. It has been shown [1] that annealing of the deposited film removes the free hydroxyls and stablilizes the P205 moiety. Densification of the film and resistance to water absorption result from the annealing process. There are a number of annealing processes for BPSG films, and it appears that any of these is compatible with the IR method. Because of variations in film densities and ratios of different oxide species present in films deposited by different reactors, it is necessary to calibrate the infrared method with some primary technique that will detect all of the boron and phosphorous present, regardless of chemical species in which it is bound. These methods include ion chromatography, wet chemical analysis, ICP, and SIMS.
FT-IR Study On Microstructure Of Diamondlike Amorphous Carbon Films
N. Nagai, M. Yoshikawa, H. Ishida, et al.
IR spectra of diamondlike amorphous carbon (DLC) films prepared by plasma CVD method have been meaured. C-H stretching absorption bands due to hydrogen bonded to sp2 and sp3 carbons were observed. The relative hydrogen content in sp2 and sp3 bonding sites can be estimated from integrated intensity ratios. It has been also manifested that the relative hydrogen content is closely related with the carbon bonding states elucidated from the Raman spectra. The ATR method is also found to be useful to analyze the microstructure of thin DLC films of low hydrogen content.
Far Infrared Spectra Of The Haloacetyl Halides
J. R. Durig, Wenyun Zhao, H. V. Phan, et al.
The far infrared spectra (350 to 35 cm-1) of a series of haloacetyl halides, CH2XCY0, in the vapor phase have been recorded at a resolution of 0.10 cm-1. The fundamental asymmetric torsional frequencies of the more stable trans (two halogen atoms oriented trans to one another) and high energy conformers have been observed and the asymmetric torsional potential functions governing internal rotation about the C-C bond have been determined. The conformation of the high energy rotamer is cis or gauche depending on the size and position of the substituted halogen. Ab initio calculations at the 3-21G, 3-21G* and 6-31G* basis set levels of the optimized geometries, potential surfaces and vibrational frequencies are used to support the conclusions made from the experimental results.
Fourier-Transform Spectroscopy Of 03 In The 3 µm Region
M. A.H. Smith, C. P. Rinsland, V. Malathy Devi, et al.
Fourier transform spectra of ozone have been recorded in the 2-5 μm region at a resolution of 0.01 cm-1. Absorption lines belonging to numerous vibration-rotation transitions have been observed in these spectra, and a detailed analysis of the band system centered at 3.6 μm has been completed.
High Resolution High Temperature Spectral Line Position Measurements Of Carbon Dioxide In The Fifteen Micron Spectral Region
Michael Hoke, Mark Esplin
Low pressure (5 Torr), high temperature (800K) gas samples of carbon dioxide have recently been studied using the high resolution interferometer and high temperature absorption cell at the Air Force Geophysics Laboratory. Our line position measurements, for the principal isotope, in the fifteen micron spectral region not only extend to high rotational quantum number many rotational vibrational bands which have been measured previously at room temperature, but also include previously unmeasured vibrational bands. Band identification and analyses of the dense spectra has been enhanced by the development of a modified Loomis-Wood graphical technique. This new graphical technique has made it easier to identify spectral lines of bands for which rotational constants are approximately known and to estimate improved values of the rotational constants once lines of the band under study are identified. Rotational constants from the Direct Numerical Diagonalization (DND) calculations of Wattson and Rothman have been found to be in good agreement with those determined from the data. The theoretical values were very useful in band assignment of spectral lines. The predictive power of the theoretical DND technique combined with the new graphical technique permitted the identification and analyses of several weak and previously unmeasured vibrational bands.
Complexes Between HC1 And Proton Acceptors In Low Temperature Argon Matrices And In Gas Mixtures
W. O. George, Rh. Lewis
The FT-IR spectra of mixtures of argon, ethene, ethyne, d6-benzene, fluorobenzene, CO, CO2, SO2, CCl4, CHC13, d6-acetone, ethanol, HCN, and Acrylonitrile in mixtures with HC1 have been recorded as gases and by matrix isolation. The features which are measured are: 1. The changes in the integrated intensity of lines in the rotation-vibration spectrum of the fundamental HC1 band as a function of nonspecific interactions with other components of the mixture. 2. Bands associated with specific interactions forming hydrogen bonded complexes in the gas and matrix isolated phase. The relationship between the two kinds of interactions is discussed.
High-Resolution Fourier Transform Spectroscopy: Line Widths And Line Shapes Of Spectral Lines Emitted From Helium And Mixed-Gas Inductively Coupled Plasmas
Akbar Montaser, I. Ishii, B. A. Palmer, et al.
Previous studies of line widths and shapes of spectral lines emitted from the inductively coupled plasmas (ICP) have concentrated on plasmas sustained in pure argon [1]. For the present study, we used the Los Alamos Fourier transform spectrometer to estimate line widths and line shapes of Fe I lines emitted from helium and argon-nitrogen ICP discharges. The effect of gas composition and plasma operating conditions on widths and shapes of the spectral lines were examined. Line widths and line shapes of Fe lines were compared with those of argon and helium for Ar ICP and He ICP discharges. Results were used to calculate Doppler temperatures and electron number densities of the cited plasmas.
Techniques Of Interactive Spectrum Analysis In High Resolution Fourier Transform Spectroscopy
Mark C. Abrams
Current methods for processing high resolution spectra center on interactive graphical displays of the spectrum on a computer and the accurate determination of line positions and line shape parameters. However, beyond the simple display of the spectrum on a computer screen, an interactive spectrum analysis program should provide an environment in which various techniques can be compared numerically. The DECOMP spectrum decomposition program is designed explicitly for the reduction of Fourier transform spectra and focuses on interactive graphical display and analysis of spectra on IBM PC compatible computers. Basic methods of spectrum manipulation will be demonstrated and a IBM PC- compatible computer will be available for hands-on demonstrations.
Time-Resolved FTIR Spectroscopy Using a Step-Scan Interferometer
A. Becker, Ch. Taran, W. Uhmann, et al.
In contrast to resonance Raman spectroscopy, there are only few reports on time resolved infrared spectroscopy (1-7). There are two main reasons: 1. infrared detectors have, as compared to UV-vis detectors, a low detectivity; 2. efficient broad-band infrared sources have usually low power. Earlier, we have developed an apparatus for infrared flash-photolysis experiments using a commercial infrared spectrophotometer as tunable monochromatic source and a photocon-ductive HgCdTe-detector. With this equipment, we were able to obtain time-resolved infrared difference spectra of CO-myoglobin (1,9), rhodopsin (10,11) and bacteriorhodopsin (11). The time-resolution could be increased up to 0.5 μs (12). But the mentioned disadvantages caused total measuring times of one day or longer. The low power of infrared sources can how be overcome by the use of quasi-continuously tunable laser sources such as CO-lasers (3) and lead-salt diode lasers (8).
Analysis Of Pulmonary Tissue Of Natural Mummy Of XIII Century (Saint Zita, Lucca-Tuscany) By Means Of FT-IR Microspectroscopy.
Enzo Benedetti, Piergiorgio Vergamini, Gino Fornaciari, et al.
During a recognition carried out by one of us on the S.Zita's body, preserved for seven hundred years in the S.Frediano's Basilica (Lucca, Tuscany-Italy) it has been possible to verify the good condition of many orgains and systems. In this comunication we report preliminary results of an analysis of the pulmonary tissue which to the histologic examination showed a typical aspect. It was observed the presence of a massive anthracosis. In order to obtain indication, at molecular level, FT-IR microspectroscopy measurements were carried out. The infrared spectra relative to different microareas allowed us to evidence regions of tissue decomposed, and others in which the infrared spectra showed absorptions characteristic of proteic components at 1650 cm-1 and 1540 cm-1 ascribed to the Amide I and Amide II vibrations respectively. In the 1350-950 cm-1 range bands due to nucleic acids were detected. Also in the CH stretching region bands due to methyl and methylene groups were observed, likely due to the presence of paraffinic segments of phospholipids of cellular membranes. Previous FT-IR studies carried out by us on biological systems such as normal and leukemic lymphocytes (1), on lymphoblast (2), and recently on cells isolated from neoplastic pulmonary tissues (3), represent a basis which allows us to perform a sufficiently complete assignment on the spectra obtained on this finding. These spectra are surprisingly very similar to those obtained by us on human lung tissue from surgical specimens. As far as we know, FT-IR microspectroscopy, which was first employed by our group in the study of human neoplasia at level of single cell (4) has been applied in the analysis of ancient pulmonary tissue, certainly not submitted to any conservative treatment. This kind of approach can open up new possibilities in obtaining indication, at molecular level, on findings of paleophanthology of different origin and age.
Micro FT-IR Characterization Of Human Lung Tumor Cells
E. Benedetti, L. Teodori, P. Vergamini, et al.
FT-IR spectroscopy has opened up a new approach to the analytical study of cell transformation. Investigations carried out in normal and leukemic lymphocytes have evidenced an increase in DNA with respect to proteic components in neoplastic cells.(1) The evaluation of the ratio of the integrated areas(A) of the bands at 1080 cm-1 (mainly DNA) and at 1540 cm-1 (proteic components) has allowed us to establish a parameter which indicates, for values above 1.5, the neoplastic nature of cells. Recently, this approach has been applied to the study of human lung tumor cells. Several monocellular suspension procedures of the tissue fragment (mechanical and/or chemical) were tested to obtain reproducible and reliable spectra able to differentiate clearly between normal and patological cells. Chemical treatment (EDTA, Pepsin, Collagenase, etc.) produced additional bands in the spectra of the cells causing distortion of the profiles of some absorptions, and as a result, mechanical treatment was preferred. The normal and neoplastic cells homogeneously distributed by cytospin preparation on BaF2 windows were examined by means of FT-IR microscopy. An examination of several microareas of each sample yielded reproducible spectra, with values of the A 1080 cm-1 / A 1540 cm-1 parameter within a very narrow range for each sample, even if certain differences still remained among the different cases, in good agreement with the results obtained for leukemic cells.(1) The value of this parameter was found to be lower for cells isolated from the normal area of lung, than in the case of those corresponding to the tumoral area, meaning that an increase occurs in DNA with respect to the proteic components. These insights, which provide a basis to obtain indications at the molecular level, can open up new possibilities in clinical practice, in order to obtain diagnosis confirmation, to detect early stages of disease and to offer additional indications in cases of dubious interpretation.
The Infrared Microscope - A Versatile And Universal Sampling Accessory.
F. J. Bergin, C. A. Gilchrist, I. Jones
In recent years the improvement in Fourier transform infrared instrumentation has led to a considerable growth in the use of infrared microscopy as an analytical tool. Many of these applications have concentrated on the spatial resolving power of the microscope for the analysis of small samples or localised contamination within a material. Recently we have been looking at some broader applications of the microscope, in particular, with respect to the non-destructive analysis of bulk polymeric materials and to its use for reflection/absorption measurements of monomolecular films on aqueous substrates. When radiation impinges on a surface the reflected light is generally considered to consist of two components. The first is termed diffuse reflectance and the second Fresnel or specular reflectance. In the case of diffuse reflectance the reflectivity is given by f(R∞) = (1-R∞)2/R∞=k/s, where R∞ is the reflectance from an infinitely thick layer and k and s are related to the absorption and scattering within the sample. Here the term k, related to the absorption, contains molecular information about the material in question. When specular reflectance dominates, the recorded spectrum bears no resemblance to an absorption spectrum but has the appearance of a first derivative spectrum. The reflectivity at normal incidence is given by R = (m-1)2/(m+1)2, where m is the complex refractive, index m = n - ik, and where n is the real component, k the imaginary component or the extinction coefficient and i is √-1 Hence the recorded reflectivity spectrum contains molecular information about the material under investigation. This molecular information can be extracted using the Kramers-Kronig transformation. The experimental system used for this study consisted of a Perkin-Elmer model 1760-X Fourier transform infrared spectrometer. A Spectra-Tech IR Plan microscope, equipped with a narrow band MCT detector and a x15 objective, was fitted to the external port. Data storage and manipulation was carried out using a 7700 series data station. For our liquid monolayer studies the samples were spread on the water surface (minimum resistivity 15 MRcm-1) from heptane solutions using a microsyringe.
Absolute Infrared Intensities Of Water-Alcohol Mixtures
John E. Bertie, M. Khalique Ahmed, Shipra Baluja
The Circle cell method for measuring absolute infrared absorption intensities has been used to study mixtures of water and methanol over the entire concentration range. We have determined values of the real and imaginary refractive indices and dielectric constants in the infrared region between 8000 and 700 cm-1, of the molar conductivity in the same region, and of the integrated areas under the molar conductivity bands. Apart from a discontinuity between 0 and 1% methanol, the latter are linear functions of mole fraction, a result that is expected for ideal solutions but not for mixtures of molecules that interact as strongly as water and methanol.
Topical Protectant Evaluation By FT-IR Spectroscopy
Ernest H. Braue, Michael G. Pannella
A unique analytical method for evaluating the effectiveness of topical protectants against penetration by chemical agents has been developed using FT-IR and the horizontal attenuated total reflectance (ATR) accessory. A template was fabricated from double-sided adhesive tape attached to a piece of plastic sheet with an 8.0mm hole punched in the middle. This laminate was placed on the surface of the ATR crystal. A uniform thickness layer of topical protectant was applied to the ATR crystal through the hole in the template. Background spectra of the ATR crystal with and without the template were recorded and stored. A chemical challenge was applied to the template filled with topical protectant, and spectra were recorded every 15 seconds using a Nicolet 60SXB FT-IR spectrometer fitted with an MCT-A detector. Analysis of the recorded spectra identified how much time was required for the chemical challenge to break through the topical protectant barrier. The method was validated using polysaturated fat, petroleum jelly, and hexafluoropropylene epoxide polymer as topical protectants. These materials were challenged with ethyl disulfide. The detection threshold concentration for ethyl disulfide in the topical protectant was observed to be 0.5% (w/w). Using a barrier thickness of 0.45mm the break-through times were observed to be 5.0 min and 22.0 min for polysaturated fat and petroleum jelly respectively. The fluoropolymer showed no break-through even after 180 min.
On-Line Monitoring Of Products Generated In The Combustion Of Polymeric Materials Using Fourier Transform Infrared Spectroscopy
Marc R. Nyden
The distribution of products which evolve during the course of a fire is sensitive to prevailing conditions of temperature, fuel composition, and oxygen availability. The dynamic nature of the combustion process has implications for the design and safe operation of controlled burning units such as municipal and hazardous waste incinerators. Spectroscopic measurements provide a means for obtaining a continuous signature of the incineration process which is suitable for input into a servo-mechanism which is designed to achieve optimal combustion efficiency. We have designed and constructed a facility for making time-resolved concentration measurements of combustion effluents. The setup consists of an FTIR spectrometer interfaced to an oxygen consumption calorimeter through a heated sample line. The gases which are evolved during the combustion of bulk materials, typically wood and plastics, are pulled through the sample line into a thermostatted gas cell at a rate of≈ 30 ℓ/min. Interferograms are co-added over 30 second intervals and processed into absorbance spectra with a resolution of = 0.5 cm-1. The concentrations for a small number of target compounds are determined from numerically robust curve-fitting techniques which make use of predetermined analytical windows and the derivative spectra obtained from a representative spectral data base. The details of our methodology and spectral data collected during the combustion of representative materials will be presented. The possibility of integrating this information into a useful model of incinerator performance will also be discussed.
FT-IR Emission Spectroscopy Of Catalysts
J. Mink, G. Keresztury
FT-IR emission spectroscopy of supported metal catalysts have been briefly summarized. Observation of low frequency bands of silica supported C5H5Fe(C0)2I has been discussed.
High Temperature Drift Spectra Measurements
Mirostaw Handke, Kazimierz Czarnecki
There are many problems in the chemistry of solids which can be solved by "in situ" high temperature IR spectra measurement. Such a measurements should be very helpful in the studies of: phase transition, formation and decomposition of solids, adsorption on solid surfaces, oxidation or reduction reaction, to name a few. Among sampling techniques used in IR spectroscopy the transmission, diffuse reflection and emission seems be useful for high temperature IR spectra measurement. The main aim of the presented paper is to show the great potential of DRIFT technique in high temperature spectra measurements under controled atmosphere. The paper also show how DRIFT accessory can be used for IR emission spectra measurements as well. The following problems solved with high temperature DRIFT technique will be discussed in the paper: - Si02 polymorphic transition - desorption of the water molecules from quartz surface, - molybdenium and vanadium oxides reduction, - phosphor - molybdenium heteropolyacid catalyst reactions. Some experimental problems concerning the high temperature DRIFT measurements will be discussed also.
Fourier Transform Spectroscopy In The Ultraviolet Range
P. H. Turner, A. Simon, R. Rubinovitz
Since we first reported on Fourier transform spectroscopy in the ultraviolet range at the Vienna FTS conference, there has been a number of instrumental development leading to improved performance in terms of signal to noise ration and resolution. Further details will be given in the poster together with some example gas phase electronic-vibrational spectra (e.g., benzene).
Performance And Applications Of A Very High Resolution Fourier Transform Spectrometer
P. H. Turner, R. Rubinovitz, A. Simon
There is an increasing need for high resolution spectroscopic measurements in areas such as gas phase molecular studies, low temperature matrices and solid state physics and environmental air analysis. In order to meet this demand, a very high resolution Fourier transform spectrometer, the IFS 120 HR has been developed which can operate from the far infrared to ultraviolet spectral ranges. The instrument incorporates a number of novel design features to enable the recording of spectra with excellent signal to noise ratio in short measurement times, high resolution achieving line widths of 0.0014 cm-1 (width at half height of CO absorption lines in the far infrared) and accurate lineshapes. Various data handling routines have been added tailored for the special requirements of high resolution spectroscopy including an extended plot package, automatic peak finder and post transform zero-filling for spectral interpolation. The poster will describe the instrument in detail and present example spectra from various fields of application.
Advantages And Use Of The Step-Scan Technique In Mid-IR FT Spectroscopy
R. Rubinovitz, J. Seebode, A. Simon
Although rapid-scan FT-IR has made many important advances in IR spectroscopy possible, it characterized by limitations that can interfere with some types of spectroscopic measurements. The first drawback is the wide modulation frequency range across the spectrum. This results since in the rapid-scan mode, modulation frequency is a function of both mirror speed and the wavelength of the IR light. Thus, difficulties may occur when studying systems involving detectors of specific, narrow bandwidths. Also, the depth profiling of photoacoustic samples can be obscured by this characteristic. A second limitation of the rapid-scan method lies in acquiring scans with sub-millisecond time resolution, since the fastest scanner can collect only about 50 scans per second at reasonable resolution. An alternative step-scan technique has been developed to deal with the above demanding applications. In this system, the moving mirror of the interferometer is "stepped" to precise locations where (using either amplitude or phase modulation) interferogram points are collected by means of lock-in amplifier. After acquisition of each interferogram point, the moving mirror is translated to the next optical retardation position. This system offers numerous advantages: Signal modulation is tunable and the same across the spectrum. This characteristic offers strong advantages in studies involving slow thermal detectors, such as photoacoustic and photothermal beam deflection spectroscopies. For repeatable events, time resolution is limited only by the speed of the acquisition electronics and detectors. Interferograms of short-lived states are collected by triggering the event of interest at each of the moving mirror's optical retardation positions and then following the response of the detector as a function of time. In this way, interferograms with time resolution of 5 microseconds or less can be collected. Finally, the step-scan system is fully compatible with a rapid-scan system, so that the user may easily switch from one mode to the other. Examples of step-scan applications will be presented and compared with corresponding spectra taken using rapid-scan methods.
Investigations Into The Chromatographic Optimization Of Combined GC/FTIR/MS
Ditmar Wulff
Even with the explosive growth and acceptance of GC/MS it has some analytical limitations. Several of these deficiencies can be overcome with information provided by GC/FTIR. Combining a GC/MS and a GC/FTIR into one system provides economies of sample, time, space, and money as well as a higher confidence qualitative result. The later results from the ability of the mass spectro -meter to give molecular fragment information with strength in homolog identification while the infrared spectrometer gives class specific-functional group and geometrical isomer data. Several configurations of the combined light pipe GC/FTIR/MS are evaluated looking toward ease of use, information content, and data evaluation. The combined system's sensitivity, chromatographic integrity, and gas chromatographic column choices and their operational parameters are discussed. The series arrangement with the GC column effluent passing through the FTIR light pipe and then serially to the MS is compared to the post column split of the column effluent to the FTIR and MS as well as to the configuration using two GC columns. Operational recommendations are given to maximize chromatographic resolution, detector sensitivity, and sample throughput. Examples are shown illustrating the combined systems operation. All parameters discussed apply to work done on the HP 5890A GC, the HP5965A IRD, and the HP 5970B MSD.
Application Of An FT-Raman Accessory Interfaced To An FT-IR Spectrometer
R. Rubinovitz, A. Simon
Raman spectroscopy is currently the focus of renewed interest due to its increasingly straightforward incorporation of near-IR laser sources and FT techniques. Conventional Raman vibrational spectroscopy provides spectral information complimentary to that obtained by IR absorption methods, thus giving the user of both techniques a more complete spectral analysis. Additionally, FT-Raman also exploits the optical throughput and wavenumber accuracy that interferometric spectroscopy offers. Still another very significant advantage results from near-IR FT-Raman's ability to obtain useful Raman spectra from compounds that would normally yield only featureless fluorescence in visible laser Raman systems. This presentation will highlight advantages that result from the coupling of a near-IR FT-Raman module with an FT-IR system. Among these is the increased sampling capability that results from the complimentary nature of the two spectroscopies. For example, although it would be nearly impossible to obtain an IR spectrum of an aqueous solution sealed in a glass tube, such a sample can be studies in quite a straightforward manner by FT-Raman spectroscopy. Also, a broad optical range is easily studied since the Raman technique allows one to observe bands corresponding to Raman shifts in the range from 3500 cm-1 down to approximately 100 cm-1 in the same scan and there is no need to change optical components. Another advantage gained by such a combined IR/Raman configuration is the resulting capability to easily switch from one technique to the other. Not only can both IR and Raman spectra be obtained routinely, but since the same data system is used by both techniques, both IR and Raman files are collected and manipulated using the same software. Thus, routines such as spectral subtraction and deconvolution can readily be applied to either technique.
On-Line FTIR Measurement Of The DEG-Content In Molten PETP Using A High Pressure, High Temperature Flow Cell.
Ralph K. Stengler, Gerald Weis
Polyester, especially polyethylene terephthalate (PETP), have a wide range of use, e.g. synthetic fibres and films. They are usually made by polycondensation of ethylene glycol and terephthalic acid. The remaining content of ethylene glycol (in, our case diethylene glycol DEG) gives an important information about the status of the polycondensation, which determines the mechanical properties of the polymer. In order to get detailed information about the PETP quality during the production it is of interest to measure and control the DEG-content in the PETP melt. During the classical preparation of a sample, occasionally there are changes in the chemical composition of the polymer (e.g. a degassing of monomers is possible). Therefore an AUTOMATIK IROS-100 infrared on-line system was used to avoid those errors since this system directly analyzes the polymer melt at the process temperature in a side-stream of the main polymer line. The molten polymer coming from a bypass of the polymer line is conveyed by a pressure controlled gear pump through a specially developed infrared cell. A special preparation of the sample is not needed. It was possible to quantify the DEG-content in PETP, which was in the range of 0.5 % - 3 %, using an infrared absorption peak with a peak location of approx. 3334 cm-1. It could be demonstrated that the moisture content of the PETP did not influence the above mentioned results. The accuracy of this method was better than 0.2 %.
Fourier Transform Infrared Reflection-Absorption Spectroscopy Of Glycine Absorbed Upon Copper
Anita Ihs, Bo Liedberg
The bonding and orientation of glycine adsorbed on copper were studied using infrared reflection-absorption spectroscopy. A comparison was made with calculated reflection-absorption spectra, which are based on the optical constants derived from the transmission-absorption spectra of the trans-Cu(gly)2.2H20- and cis-Cu(gly)2-H20-complexes. Copper films prepared at three different evaporation rates were also studied in order to determine the influence of preferred film orientation and grain size on the chemical structure of adsorbed glycine. The results obtained indicate that the glycine molecules form a physisorbed and anhydrous layer of Cu(gly)2-complexes on the surface.
Infrared Microspectroscopy Of Pathologic Tissue
Timothy J. O'Leary, Walter F. Engler, Kathleen M. Ventre
Infrared spectroscopy is a powerful technique by which to characterize the conformations of proteins, lipids, and nucleic acids (1). Previously we have demonstrated that infrared spectroscopy can be used to characterize the secondary structure of abnormal protein accumulation products, known as amyloid, which are often found in association with medullary carcinoma of the thyroid (2). The utility of the technique was highly limited by the fact that essentially the entire specimen had to consist of this abnormal protein for infrared spectroscopic analysis to be useful. The development of high quality microscopes capable of both light microscopic and infrared characterization of materials has enabled us to extend our earlier use of infrared spectroscopy to diseases and tissues in which the abnormal region of interest is only a few hundred square micrometers in area. Tissue for spectroscopic examination is mounted on microscope slides which have been prepared by acid washing, plating with gold or gold-palladium alloy (3) and coating with high molecular weight poly-L-lysine. Sections of tissue which have been previously embedded in paraffin are cut with a microtome at 4 to 5 micrometers thickness, floated onto a bath of distilled water, picked up on the microscope slide, and allowed to dry overnight. Paraffin is removed by soaking the slides in two changes of xylene, and then the sections are rehydrated by placing them in absolute alcohol, then in fifty percent alcohol, and finally in water. Sections may then be stained using standard histologic stains, such as hematoxylin and eosin, then once again dehydrated with alcohol. After drying, the sections are covered with an index-matching fluid, such as Fluorolube, which allows a relatively good visual microscopic examination of the tissue when the microscope is used in reflectance mode. High quality reflectance infrared spectra may be easily obtained when the tissue is prepared and mounted in this way (Figure 1). Alternatively, fresh or formalin-fixed tissues which have not been embedded in paraffin may be prepared for examination by freezing them in a cryostat, cutting five to ten micrometer thick sections, and mounting them directly on the polylysine coated gold-plated slides. These tissues may then be stained with hematoxylin and eosin or with Diff-Quik, then dehydrated with acetone, thus preserving cellular lipids. We have examined a number of cases of medullary carcinoma of the thyroid and obtained infrared spectra of the associated amyloid protein. Spectra were obtained using an IR-Plan microscope interfaced to a Bomem DA3 Fourier transform infrared spectrometer. A 32x objective was used, with a circular aperture which allowed acquisition of spectra from a region as small as 90 micrometers in diameter. A narrow-band 0.25 mm MCT detector was employed. A typical spectrum from amyloid found i11 a medullary carcinoma of the thyroid is found in Figure 1; features found in the 1630 to 1645 cm region of the Amide I band are indicative of β-sheet structure, which has previously been described in amyloid proteins (4). The amount of fl-sheet structure, as assessed visually in comparison with the rest of the Amide I band, varies markedly from region to region and case to case. The presence of this βsheet structure cannot be used to differentiate amyloid from other extracellular proteins. Figure 2 shows the spectrum of colloid from a thyroid follicle. This material, which is largely composed of thyroglobulin, also shows a significant amount of βstructure, as does the heart muscle examined following frozen section. In the case of the heart muscle, however, cellular lipid is also observed as methylene C-H stretching modes in the 2800-3100 cm region of the spectrum. The frozen section tissue preparation procedure leaves the cellular lipid in place, while the paraffin-embedding and removal procedure used for preparation of the first two specimens extracts cellular lipids as well, resulting in a much less prominent C-H stretching mode region.
FTIR Spectroscopy Evidence Of Native Cellulose 1 Allomorphism
S. Yu Maslov, D. A. Sukhov
Some native celluloses belonging by diffractometric data to form 1 (Cl) possesses essentialy different 13-C NMR spectra [1]. In this report we present evidence that significant differences in Far IR spectra of Cl specimens diverse in nature have been found. In the Fig.one can see Cl spectra of cotton (top) and Valonia macrophisa twice narrowed by Fourier self-deconvolution method.
Spectral Lineshape Functions For Off-Axis Detectors In Michelson Interferometers
Marshall H. Bruce
The increasing use of detector arrays in Fourier Transform Spectroscopy requires an understanding of the line shape spectral shifts and distortions inherent in using off-axis sensors. For rectangular, sector, and circular shaped detectors a compact formulation is presented for calculating these factors without the necessity for numerical modeling.
Supercritical Fluid Chromatography/Fourier Transform Infrared Spectroscopy Of Food Components
Elizabeth M. Calvey, Samuel W. Page, Larry T. Taylor
Supercritical fluid (SF) technologies are being investigated extensively for applications in food processing. The number of SF-related patents issued testifies to the level of interest. Among the properties of materials at temperatures and pressures above their critical points (supercritical fluids) is density-dependent solvating power. Supercritical CO2 is of particular interest to the food industry because of its low critical temperature (31.3°C) and low toxicity. Many of the components in food matrices react or degrade at elevated temperatures and may be adversely affected by high temperature extractions. Likewise, these components may not be amenable to GC analyses. Our SF research has been in the development of methods employing supercritical fluid chromatography (SFC) and extraction (SFE) coupled to a Fourier transform infrared (FT-IR) spectrometer to investigate food composition. The effects of processing techniques on the isomeric fatty acid content of edible oils and the analysis of lipid oxidation products using SFC/FT-IR with a flow-cell interface are described.
Real-Time Measurement Of Polyurethane Foam Reactions And Hydrogen-Bonding By FT-IR Spectroscopy
B. L. Davis, M. A. Harthcock, C. P. Christenson, et al.
The reaction and hydrogen-bond formation kinetics which occur in polyurethane foams will have an ultimate effect on the properties of these materials. Measurement of several urethane and urea carbonyl absorptions (free and hydrogen-bonded) provides two important pieces of information: (1) the chemical reactions which occur and (2) the progression of hydrogen-bond formation after reaction has completed. An attenuated total reflectance (ATR) Fourier-transform infrared spectroscopic technique has been previously developed which allows real-time data to be obtained during the foaming reaction 1,2. The authors have adapted a similar system to studying foams in order to more quantitatively interpret the real-time data in terms of the complex hydrogen-bonding structure. The vibrational assignments used for the carbonyl region of polyurethane foam spectra are as follows: 1732 cm-1 free urethane 1712 free urea 1701 ordered hydrogen-bonded urethane 1699-1653 monodentate hydrogen-bonded urea (Fig. 1) 1641 bidentate/ordered hydrogen-bonded urea. (Fig. 1)
Infrared And Visible Spectra And Magnetic Properties Of Sodium And Potassium Bis(2,4-Pentanedionato) Selenito Cobaltate (II) And Nickelate (II), Complexes
Salah B. El-Maraghy, Kamal R. S., Shaker L. S., et al.
Inorganic anions are commonly used as ligands in coordination chemistry (1, 2). The properties of the selenite anions in aqueous solution are important in determining selenito complex formation. In dilute aqueous solutions, selenous acid is dibasic (K1 = 4 x 10-3; K2 = 10-8 )forming HSe03 and Se03 anions. At higher concentrations, extensive dimerization occurs with these species to yield-H(Se 02) 3 2 H2 (Se03)2 2 , H3(Se 03)2 and H4(Se 03)2. Limited information is available about the selenite group as a ligand in coordination chemistry. A general survey on the preparation and structure of selenites and mixed selenito complexes of transition metals will be represented later on. The study of the I.R. modes of the selenite group in these complexes is still lacking although the X-ray structure of some normal selenites is already established. Also, the magnetic behaviour of these complexes needs furtehr investigation and study. The structure of these complexes will be deduced from their visible spectra, magnetic moments and I.R. spectra.
Palladium (II) Hydrazopyrazolone Complexes
Salah B. El-Maraghy, K. A.R. Salib, S. L. Stefen
Palladium (II) complexes with 1-pheny1-3-methy1-4-(arylhydrazo)-5- pyrazolone dyes were studied spectrophotometrically. Pd (II) forms 1:1 and 1:2 complexes with the ligands by the replacement of their phenolic and hydrazo protons. The ligands behave as tridentate in the 1:1 complex and as bidentate in the 1:2 complex. The sability constants of these complexes are dependent on the type of substituents in the benzene ring of the arylazo moiety.
Raman Spectroscopy Of Stressed Samples Of Oriented Poly(Ethylene Terephthalate)
L. J. Fina, D. I. Bower, I. M. Ward
Measurements of the shift and change of shape of the 1616 cm-1 Raman scattering peak of two moderately oriented samples of poly (ethylene terephthalate) (PET) under tensile loads of up to 0.2 GPa are reported, together with the corresponding strains. To obtain reproducible results, load cycling procedures were adopted similar to those established for the study of viscoelastic behaviour. The Raman scattering was observed with polarized incident and scattered light, with the polarization directions either both parallel or both perpendicular to the draw direction in the samples. The results showed that for both samples the Raman shift was linearly related to the applied stress below the yield point. Up to the yield point very little change of line width was observed, but above the yield point the width increased significantly. Differences in both widths and shifts were observed for the two polarization directions at the same stress level. The results are discussed in terms of the usual assumptions that the shift of the line gives a measure of the average stress in those chains which predominantly contribute to the peak and that the width and shape of the line give information about the spread of stresses. It is concluded that the technique can give useful information about the molecular stress distribution in thick samples of moderately oriented PET under load, including information about the different stress distributions on chains at different angles to the draw direction.
Relationship Between Infrared Intensity Theories: Electro-Optical Parameters And Bond Polar Parameters
B. Galabov, T. Dudev
Mathematical and physical aspects are analysed of the relationship between two theoretical formulations of infrared intensities employing parameters associated with chemical bonds: the valence optical theory and bond polar parameters method. Parallel applications of the two theories in analysing experimental IR intensity data for methylchloride are presented.
Improved Far Infrared Vibrational Spectroscopy Of Gap: An Exacting Test Of Theory
S. B. Upadhyay, G. A. Gledhill, R. C. Newman
GaP was one of the first III-V compounds to be studied successfully by infrared spectroscopy. One reason for this was that many impurities which were of technological importance produce strong localised vibrational modes (LVMs) in spectroscopically convenient positions in this material. This is true both for simple substitutional impurities and for more complicated centres involving intrinsic defects.1,2 A more detailed infrared study of GaP is valuable for two reasons: first that it can provide useful information about corresponding defects in other III-V compounds such as GaAs which are technologically important but less amenable to spectroscopic study and second, it provides a wide range of data for the testing of theoretical models. This is because GaP, unlike GaAs has a gap in the one-phonon density of states so that a substitutional impurity such as B on the Ga site will exhibit three modes of vibration for each of its isotopes (a localised vibrational mode, gap-mode and a low frequency resonance). To predict the frequencies of these modes correctly, together with the correct frequency separation for the isotopes, is indeed an exacting test of theory3. Unfortunately, early spectra of gap modes in boron doped GaP were made with inferior spectral resolution and signal/noise ratio 1,2,4, with the result that information was misinterpreted,4 or the correct interpretation1,2 ignored, possibly due to the lack of convincing spectra. Our aim is to remedy this situation in particular as part of a presentation of improved spectral data recorded at 15K over a wide frequency range, and to give more precise values for the frequencies of modes commonly used in the testing of theoretical models. In the course of this we have been able to search for previously unreported LVMs.
High Resolution FTIR Study Of Lvms Due To C In GaAs: Measurement Of Internal Strains And Structure Of The C(1) Lines
G. A. Gledhill, S. B. Upadhyay, M. R. Brozel, et al.
FTIR vibrational spectroscopy is a technique which is widely used in characterising defects in semiconducting crystals. The approach has usually been to measure the line strengths of the localised vibrational modes (LVMs) in a series of samples in order to identify the defect centres from which they arise. With improvements in instrumental resolution and detectivity, the emphasis is now on analysing the structure and measuring the widths of LVM-lines. The width of these lines is limited to ~1 cm-1 for samples at room temperature but on cooling to below 100K some lines will be considerably sharper. The width is then limited by both the isotopic distribution of the nearest neighbours of the impurity atom and the internal strain present in the sample. It is this relationship which we shall examine here, generating internal strain by fast particle irradiations in samples which have a very small intrinsic internal strain. Consider carbon impurity in GaAs situated on the As lattice site; its four next nearest neighbours will be Ga atoms. Naturally occurring Ga has 60% of isotope of mass 69 and 40% of mass 71, so different line positions will result from the various combinations of isotopes of the nearest neighbours of the C atom. This structure, first observed by Theis et al.1 for the CAs line at 583 cm-1 has been satisfactorily fitted using a simple model2. If it is assumed that lattice strain is a measure of crystal quality, then the extent to which the anticipated structure is present on a line, such as the CAs LVM, can be used as a measure of the quality of the crystal. Thus, provided all measurements are made at the same temperature and spectroscopic resolution, it is possible to assess crystal quality in terms of an equivalent dose of radiation on a crystal of low internal strain which would produce the same,degradation of line structure. It has been shown previously 3,4 that after electron irradiation of carbon doped samples there is a reduction in the integrated absorption from CAs acceptors due to the capture of an arsenic interstitial and a corresponding growth of lines on either side of the CAS line due to the carbon complex formed. The irradiation induced lines, previously designated C(1)-lines are at 577 and 606 cm-1. Although the samples used for the previous measurements contained much more carbon than the present sample, they were of inferior quality, with the result that some of the structure which might otherwise be present was broadened out due to the intrinsic internal strain.
SI, The Quantitative Measurement Of Distortion Of Smoothed Fourier Transform Infrared Spectra
Wang Jin Hai
The smooth is an effective function of data process to improve the quality and the S/N ratio of FTIR spectra. Unfortunately, the smooth results in simultaneously the distortions of spectra and the loss of valuable spectral information in different extent. How many will the distortions be? How can we reduce it? No systematic research was reported up to now [1-- 4,6]. This paper presents the primary answer. Like smooth effect, distortion is proportional to the number of points (Np) and the number of runs (Nr). The distortions include the decrease of absorbance intensity, the disappear-ance of some small and/or shoulder bands and the shift of some bands to higher or lower +requencies C53. A function of smoo-th index (:r) can he used to measure the distortion extent which is de.fined for the first time by the follownd empiric formula:
FTIR Studies Of Molecular Assemblies On Solid Surfaces
V. M. Hallmark, L. B. Shih, P. Stroeve, et al.
The first observation of spontaneous assembly from solution of a well-ordered polymer monolayer is reported for the system poly(1-octadecene-co-maleic anhydride) adsorbed from ethanol solution onto silver substrates. Analysis by grazing incidence reflection infrared spectroscopy suggests that these monolayers compare quite favorably in terms of orientational order with Langmuir-Blodgett films made from the same material. Thermal stability of these films is significantly enhanced compared to analogous monomeric monolayers of fatty acids.
Functional Group Imaging: Methods, Experimental Considerations, And Applications
Matthew A. Harthcock, Bradley L. Davis, Scott Nitzsche
Functional Group Imaging (FGI) is a technique by which an image of a material can be generated based on the functional groups which absorb infrared radiation. Spatially specific infrared spectra are obtained using infrared microspectroscopic methods and a mapping stage which is interfaced to the FT-IR's data system.1-3 The absolute spatial resolution possible is currently diffraction limited and thus a function of the wavelength of the infrared radiation.
High Resolution Fourier Transform Spectroscopy In The Far Infrared
Dieter Hausamann
The resolution of Fourier transform spectrometers has been considerably improved within the last years, optical path differences of 6 m and above being now commercially available. The Far Infrared Group of the German Aerospace Research Est. is involved in research activities concerning trace gas analysis in the upper atmosphere. Starting point of our investigations is the laboratory spectroscopy of environmentally relevant trace gases, e.g. fluorocarbons, with a high resolution Fourier transform spectrometer. First results for the pure rotational spectrum of CHF3 (Fluoroform) will be presented. The high instrument resolution (ca. 0.0012 cm -1 the FIR) allows very precise determination of molecular constants. Nevertheless, there are some severe problems related to the increasing resolution of FT instruments, especially in the Far Infrared. Phase errors, line asymmetries and other deviations from the ideal case make it very difficult to determine the exact line position as well as to calibrate the intensity scale: absolute line intensities, however, are an essential information for the spectroscopist as well as for the environment analyst who wants to know absolute concentration and detectability limits for pollutants.
Fourier Transform Spectra Of Alkali Metal Impurities In Silicon And Germanium
L. T. Ho
It has been found that alkali metal elements can be diffused into silicon and germanium. The infrared absorption spectra of these impurities have been measured using a Fourier transform spectrometer. Unlike the donor behavior of lithium in both silicon and germanium, the spectra of sodium show that it is a donor in silicon while an acceptor in germanium. It has also been found that the sodium spectrum in silicon is strikingly similar to that of lithium. Possible reasons for this unexpected result are discussed.
Application Of FFT In Phase Correction And Mathematical Filtering
Petri Jaakkola
A method employing FFT to compute the convolution arising when filtering and phase-correcting one-sided interferograms is presented. Particular attention is paid on calculation of long data arrays. Efficiency and accuracy of the method is tested with generated interferograms.
Compact Multichannel FTIR-Sensor With A Savart-Plate Interferometer
S. Kawata, Y. Inouye, S. Minami
Several years ago we invented a new type of Fourier-transform spectrometer using a shearing interferometer and a multichannel detector 1 ,2. Since this type of spectrometer contains no mechanically moving parts, it has many potential applications including a compact-size FTIR sensor for field-use and time-resolved spectroscopy of fast or transient phenomena. We have investigated several types of common-path interferometers with particular emphasis on easy optical alignment, durability, and ruggedness1-5. In this paper, we propose a new multichannel FTIR system with an extremely high optical throughput, which may prove optimal for field-use sensor applications.
Influences Of Surface Reflection On Diffuse Reflectance Measurements
E. H. Korte, H. Staat
When the diffuse reflectance of samples with smooth surfaces such as varnishes, surface coatings, films etc. are to be measured, the regular (Fresnel) reflection at the surface can interfere in three ways: 1. If the regular reflected radiation reaches the detector, its dispersivelike features are superimposed on the diffuse reflectance spectrum; the resulting distortions are particularly severe, when the diffuse reflectance is low. 2. The regularly reflected radiation cannot contribute to the diffuse-reflection process, thus causing a baseline error. 3. Upon reaching the surface after having been diffusely reflected, the radiation is subjected to regular reflection again. Different from case 1, all angles of incidence are now possible so that even total reflection occurs. Since the reflected radiation undergoes the diffuse-reflection process again with the same probability of being ab-sorbed as before, the overall radiation emerging from the sample is decreased and this the more, the stronger an absorption band is. Results of calculations and experiments will be given and discussed.
FTIR And TGA/FTIR Characterization Of A Polyethylene Photodegradable Concentrate
T. Kumar, D. J. Johnson, D. A.C. Compton
An integrated thermogravimetric/Fourier transform infrared (TGA/FTIR) system is used to detect the presence of a fatty acid in a commercial, photodegradable, polyethylene concentrate. This technique is simple, rapid, convenient, and requires minimal sample manipulation. It can be very useful for monitoring the differences in resin concentrates. Results from FUR and TGA/FTIR experiments are presented.
Regularity Bands Behaviour In Infrared Spectra Of Polymers With A Partly Disturbed Regular Structure
I. V. Kumpanenko, N. V. Chukhanov
The behaviour of some of the regularity bands in IR spectra of polymers with a partly disturbed regular structure has been studied. According to the original Zerbi's classification the regularity bands may be assigned to the most IR activated vibrational state densities of individual regular segments in irregular polymer chains. In the case of the finite length regular helical (rim) macromolecules these bands are the superpositions of the overlapping more or less activated chain vibration bands concentrated near0.0 or0.2irm/n phase differences for adjacent repeat units equivalent atoms vibrations. The specific feature of many of these bands is their monotonic intensification and rather rapid approach of band peak intensity I to its limit value with the increase of the number of repeat units N in regular segment. The growth of I is due to both the increase of the integral intensity and the decrease of the bandwidth F. In some cases the peak frequencies of these bands either do not or only weakly depend on the regular segment length. General simple ex-pressions for the bandwidth and intensity dependences on N for these bands in terms of the repeat unit normal coordinates displacements have been obtained. For non-correlated chain mode coupling the expressions have been reduced to 11oc(T/N)1/2 and I ocN1/2(1-N /N) , respectively, where T is the temperature. The relations obtained have been applied to the study of the microstructure and IR spectra of styrene-styrene--d1, tetrahydrofurane-propylene oxide, ethylene -butene-1 and ethylene oxide-propylene oxide homo and block co-polymers. It is argued that the regularity band intensity carries information about the regular segment mean lengths and length distribution in homo and copolymers.
Applications Of Step-Scan Interferometry
Christopher J. Manning, Jeffrey M. Widder, Richard A. Palmer, et al.
Interferometry, in combination with the Fourier transform, is a powerful tool for IR spectroscopy. However, most commercial MIR spectrometers are not well suited to measuring spectra of dynamic systems. This disadvantage is due to the rapid scan mode of operation, in which the scanning mirror of the interferometer moves at constant velocity, v. As a consequence, each IR wavelength, λ, is modulated with its own Fourier frequency (f = 2v/λ). This time dependent modulation of the IR, caused by the rapid scan, becomes increasingly more difficult to separate from time dependent variations of the IR intensity caused by a dynamic system under study, as the time resolution desired approaches the Fourier modulation periods. A convenient solution to this problem is the use of step-scan interferometry. In this mode of operation, the moving mirror of the interferometer is stopped at evenly spaced intervals of the HeNe reference laser interference pattern while data are collected. As a consequence, the IR light is not modulated by the interferometer, and temporal intensity variations can be related to the dynamic system under study. Applications include photothermal/photoacoustic spectroscopy, phase-resolved spectroscopy, and classic time-resolved spectroscopy (i.e., pulsed excitation).
Design Principles And Instrumentation For Step-Scan FTIR
Christopher J. Manning, Richard A. Palmer
Step-scan, or step-by-step data collection in optical interferometry historically preceeded the rapid-scan method currently favored by commercial FTIR instrument manufacturers. Although rapid-scan data collection with opto-electronic sampling control has clearly been the key to the dramatic revival of FTIR, and of infrared spectroscopy in general, there are some experiments for which a return to step-scan techniques is a definite advantage. These include particularly experiments in which time resolution in the range of rapid-scan Fourier modulation periods is desirable. Step-scan FTIR differs from rapid-scan FTIR in the control of the mirror position and the timing of data collection. The rapid-scan mode involves moving the mirror continuously, and triggering data collection at evenly spaced intervals of the HeNe reference laser interference pattern. A particular advantage of rapid scanning is that minor fluctuations in the velocity of the mirror are compensated for during sampling. In contrast, with step-scan operation the mirror is stopped at, or vibrated about, each data collection point. This has the effect of uncoupling the spectral multiplexing from any temporal aspects of the experiment and makes step-scanning applicable to a wide range of dynamic spectroscopy. However, fluctuations in the mirror position are not easily compensated for and contribute to noise in the transformed spectra. The minimization of such sampling errors is the central challenge of step-scan interferometry.
Problems And Caveats Associated With The Determination Of Protein Conformation By FT-IR Spectroscopy
H. H. Mantsch, W. K. Surewicz, A. Muga, et al.
Infrared spectroscopy is being used increasingly to study the conformational structure of proteins and polypeptides in aqueous solution. The methodology generally used for the infrared spectroscopic analysis of protein secondary structure is based on three steps: 1. Separation of the overlapping amide I (amide C = O stretching) component bands via band-narrowing procedures such as Fourier self-deconvolution or derivation. 2. Assignment of the resolved component bands, based on previously established spectra-structure correlations, to different secondary structure elements, i.e., alpha helices, beta-sheets, turns or non-ordered conformations. 3. Extraction of quantitative information on protein secondary structure from analysis of amide I band profiles by curve fitting. Each of these three steps has potential sources of error which have to be recognized to prevent fallacious interpretations.
High Resolution Infrared Spectra Of Vi And V3 Of Nitrogen Trifluoride
Joseph K. McDonald
With the high resolution Fourier transform spectrometer now available the vibration-rotation spectra of many of the heavier molecules can now be resolved. In previous mid-infrared rotation analysis of the fundamentals of nitrogen trifluoride (NF3) resolutions ranging from 0.05 to 0.2 cm-1 were used (1,2). The high resolution Fourier transform spectra of v1 and v3 have been recorded with a Bomem interferometer with an apodized resolution of about 0.004 cm-1. The v1 parallel band is centered at 1032 cm-1 and has the classic appear-ance of a parallel band with small changes in the rotational constants. The higher resolution spectra reveals the K structure in the different branches. From the intensity alternation, definitive numbering of the K branches could be obtained and more accurate rotational and distortion constants obtained from the rotational analysis. The v3 perpendicular band is centered at 909 cm-1 . With the higher resolution spectra the rotational structure that is observed under lower resolution is shown to be due to the PQ branches. The RQ branches are not apparent. The large intensity variation in the Q branches is due to ℓ-type resonances. The intense PQ branches versus weak RQ branches indicate that the Q,-type doubling constant q3 is negative, as calculated earlier (3,4). The ς3 constant (.81) determined from the sum rule is too large to explain the smaller separation observed (6.4 cm-1 versus 4.7 cm-1). A strong Coriolis perturbation is indicated, probably with the 2v4 (A1) vibration at 984 cm-1. The analysis of this vibrational band is in progress and will be reported.
Development Of Mid-Infrared Fiber Optics For Spectroscopic Applications
Robert G. Messerschmidt, James A. Harrington
The optical literature indicates that there has been much research into the fabrication and testing of infrared fiber optics (IRFO's) (1-6). Unfortunately for the spectroscopist, the majority of the research has been toward the goal of low-loss communications fiber applications. This application does not require transmission out into the fingerprint region of the mid-infrared. The chalcogenide glasses such as germanium:arsenic:selenium solutions, and heavy metal fluorides such as ZrF4 have received the most attention. There are several classes of materials which have been rejected for communications use, which would work quite well as spectroscopic or thermal energy relay systems, if the mechanical requirements are not too stringent. Some of these materials are now starting to be used in spectroscopy (7). This poster will detail progress with two types of metal halides. Specifically, we have produced fibers from silver bromide/chloride and potassium bromide/chloride. The latter is a core:clad structure. The fabrication methods employed are similar to methods described in the literature (8). These metal halide fibers are polycrystalline (pc) in structure. Of particular interest are the alkali halides (9) which can theoretically have very low scatter, due to their low refractive index and high purity.
Identification Of Fatty Acid Isomers By Gas Chromatography / Matrix Isolation / Fourier Transform Infrared Spectroscopy
Magdi M. Mossoba, Richard E. McDonald, Jo-Yun T. Chen, et al.
Geometric and positional isomers of fatty acid methyl esters (FAME) derived from hydrogenated soybean oil and margarines were separated by silver nitrate-thin layer chromatography (AgNO3-TLC) followed by capillary gas chromatography (GC) and identified by matrix isolation / Fourier transform infrared (MI/FTIR) spectroscopyi,2. Because of the high specificity of the MI technique, it was possible to distinguish between different 18-carbon aliphatic chains of FAME positional isomers with cis or trans configuration, and to determine their degree of unsaturation. For the first time mid-IR spectra were observed for methylene-interrupted or isolated trans, trans or cis/ trans C18 FAME positional isomers. These spectra could be readily differentiated based on unique MI/FTIR spectral characteristics.
Low-Temperature (75 To 400°C) Oxidation Study Of Coal By Diffuse Reflectance Infrared Fourier Transform (DRIFT) Spectroscopy
N. R. Smyrl, E. L. Fuller Jr.
In situ low-temperature air oxidation studies of subbituminous coal have been performed at 77, 125, 200, 300, and 400°C by diffuse reflectance Fourier transform (DRIFT) spectroscopy. The oxidation reaction proceeds via oxygen insertion at aliphatic sites in the coal structure, which progressively produces aldo/keto groups, acid groups, and acid anhydride entities with the simultaneous consumption of hydrogen at these sites. The production of anhydrides occurs even at the lowest temperature (77°C), but only above 200°C is there sufficient mobility of the acid functionalities for major quantities of the anhydride species to be formed. Above 400C, the anhydro groups predominate in the steady-state production of carbon dioxide and water vapor. In addition to the detailed information concerning the carbonyl species, the spectra of the oxidized coal reveal some new information regarding the aromatic C-H stretching bands, which can be studied in some detail unencumbered by interference from the aliphatic bands that have been removed in the oxidation process. Further details related to the aromatic bands are revealed by deuterium exchange of the remaining 0-H groups (primarily phenolic type 0-H) in the oxidized coal structure. This exchange removes these bands from overlap with the broad 0-H stretching band resulting from hydrogen bonding of the 0-H groups. The present study reveals further merits of in situ DRIFT analysis in extending the knowledge of coal structure and reactions. The study also indicates much potential for further work.
Automated Chemical Quality Control Using FTIR
James F. Sprouse
Automated chemical quality control of raw materials as they enter the manufacturing plant has been achieved using Fourier Transform infrared Spectroscopy (FTIR), an appropriate sampling method, and analysis software which controls the FTIR and performs automated data analysis. An infrared spectrum of a raw material is measured, then compared with that of a premeasured reference material in order to detect a contaminated, or out-of-specification, raw material before it enters the manufacturing process. Automated data analysis is achieved using a three tiered search algorithm which combines results from a high resolution (16 bit) Euclidean Distance search with those from both a forward and reverse peak search in order to detect a contaminated raw material. Spectral comparisons are made with a small user-generated reference library of in-spec raw materials. The quality control criteria will be presented, along with an application example, based on: (a) sampling technology; (b) IR spectrum measurement; (c) Data Analysis; (d) Data and Information Management; and (e) Results Reporting.
Fourier Transform Infrared Emission Measurements By Exciting With A Laser
Norio Teramae, Tsuguo Sawada, Shigeyuki Tanaka
Infrared emission spectroscopy(EMS) has been known as an useful method for analysing thin organic films on metal substrates which have high reflectivity[1,2]. However, it is difficult to obtain spatial resolution of a specimen, since the measurement by the conventional method is carried out by heating the sample above detector temperature using an electrical heating equipments. In this paper, a laser excitaion method was examined instead of using an electrical heater. The emission spectra of organic compounds on aluminum plates were measured by illuminating the specimen continuously with a laser beam, and the results were comapred with the spectra obtained by a conventional heating method. Preliminary results obtained by a step scan FT-IR spectrometer and a modulated laser beam were also discussed.
A Cryogenic Infrared Dual Optical Channel Interferometer-Spectrometer For Upper Atmospheric Measurements
V. Alan Thurgood, Ronald J. Huppi
A cryogenically cooled dual optical channel interferometer-spectrometer is being developed by the Space Dynamics Laboratory at Utah State University (USU). The design presented is based on a standard Michelson interferometer implemented on a flexural pivot parallelogram carriage with dual beam splitters and a single drive system. The sensor will be used to make simultaneous measurements of atmospheric emissions in the 2- to 22-μm spectral range from a rocketborne platform. The dual optical channel design allows optical materials and throughput to be optimized for narrower spectral ranges, resulting in improved performance. Other enhancements resulting from the use of a dual optical channel over the single channel design are presented.
FT IR-Spectroscopy And Quartz Surface Polariton Splitting By Ion-Implanted Layer
G. N Zhizhin, K. T. Antonova
Me optical properties of ion implanted (200 KeV, N+ions, doses 8x10 13-3x10 16 ion. cm-2) and thermal annealed (700C) quartz are investigated using a Fourier-transform spectrometer BOMEM MICHELSON 110. A dispersion analysis and surface polariton-spectroscopy were used to determine the optical constants of the damaged transition surface layer. The influence of dose is studied and a comparison is made with the properties of the samples before annealing.
FT-Raman Spectroscopy Of Thin Films By Integrated And Fiber Optics Techniques
C. Zimba, V. Hallmark, J. Swalen, et al.
Structural studies of thin films containing chromophores have not been possible using Raman spectroscopy with visible excitation due to the presence of fluorescence which results when visible photons are absorbed by the chromophores. To circumvent this problem FT-Raman instrumentation has been developed so that spectra can be obtained with excitation at 1.064 microns, much too low in energy for fluorescence to occur. Integrated optical techniques which have been successfully used to investigate thin films at visible wavelengths has been adapted to the FT-Raman instrumentation with certain modifications. The primary change occurred in the collection optics where the imaging of the laser streak in the film upon the circular entrances aperture of an FTIR yielded a poor S/N spectrum of a thin polymer film. The geometric mismatch of streak image and circular aperture was rectified by the use of a fiber optic image converter. This consisted of a fiber optic bundle which had a linear array of fibers on one end for collection of light from the streak and a circular array of fibers on the other end so as to maximize the amount of light that entered the FTIR. A significant improvement in spectral quality was observed. Feasibility studies of guest/host interactions in thin composite films containing chromophores have been demonstrated and the results for a dye/cellulose acetate film will, in particular, be discussed.
Direct Determination Of Conformational Disorder In Biological Membranes By FT-IR Spectroscopy
Richard Mendelsohn, Mark Davies, Herbert F. Schuster, et al.
Although the determination of conformational disorder in biological membranes is an important goal of current membrane biophysics, a quantitative formulation has remained elusive. The current study describes a successful determination of trans-gauche isomerization at specific depths in phospholipid bilayers. The approach was suggested by Snyder and Poore (1) and utilizes the CD2 rocking modes of specifically deuterated hydrocarbons as conformational probes. This CD2 probe frequency is dependent on the conformation of the C-C-C skeleton of which the central carbon atom contains the CD2 moiety. The various conformations give rise to discrete (but weak) bands in the IR, as summarized below:
Gc/Matrix Isolation/FTIR Studies Of Decompositon Products Of Irganox 1010 In An Aqueous Ethanol System
J. T. Chen, M. M. Mossoba, S. L. Varner, et al.
Irganox 1010 is an antioxidant used in food packaging. The degradation products of Irganox 1010 in a 50% aqueous ethanol system at 90C were examined by GC/MS and GC/MI/FTIR. The data suggest Irganox 10101 is hydrolyzed to form (3) benzenepropanoic acid, 3,5-bis (1,1-dimethylethyl)4-hydroxy-which reacts with solvent ethanol to form (f) its ethyl ester. The 4 other decomposition products (a) 2.5 cyclohexadiene-I,4-dione, 2,6-bis(1.1-dimethylethyl)-; (B) 3.5-bis-(1,1,-dimethylethyl)-2.5 cyclohexadiene-4-one spiro (5'-tetrahydrofuran-2'-one); (C) benzofuran, 2,3-dihydro-3.3-dimethyl-5 ethenyl-7-(1,1-dimethylethyl)-and (D) benzaldehyede, 3.5-bis-(1,1-dimethylethyl)-4-hydroxy-, can result from osidation, dehydration and decarboxylation processes of (E).
Applications Of Fourier Transform Raman Spectroscopy To Highly Unsaturated Phosphatidylcholine Multilamellar Membrane Assemblies.
E. Neil Lewis, Burton J. Litman, Ira W. Levin
Although the use of visible laser excitation in dispersive Raman spectroscopy is well documented in studies characterizing model membrane preparations composed of lipids with saturated acyl chains, applications of this technique to bilayer assemblies containing highly unsaturated acyl chains are limited due to the tendency of the latter lipids to undergo peroxidation, with the production of potentially fluorescent decomposition products. These lipids represent important constituents of mammalian cell membranes, as demonstrated, for example, in the retinal rod outer segment disc membrane which contains approximately 50% of its phospholipid acyl chains as docosahexaenoic acid (22:6). A method for avoiding the pernicious fluorescence associated with these types of materials involves a relatively new approach coupling the multiplex, throughput and precise frequency measurement advantages of a Michelson interferometer with a near-infrared Nd:YAG laser source and a high sensitivity detector. In this study we use FT-Raman spectroscopy to examine the packing and dynamic properties of multilamellar lipid assemblies composed of various unsaturated lipids containing acyl chains with one, four and six double bonds, respectively, in an attempt to relate the inter- and intramolecular properties of the lipid matrix to the degree of chain unsaturation. The results suggest that increased unsaturation in the sn2 acyl chain of the phospholipid molecules with a completely saturated sni chain leads to increased bilayer order with a concomitant increase in the degree of rotational freedom for the sn2 chain.
Effect Of Diffraction In High Resolution Ftir-Spectrometers
Kauko Salonen, Jyrki Kauppinen
Utilizing the cube-corner mirrors in FTIR-spectrometers has rendered possible to record the interferogram over very long mirror displacements and extend the best resolving power to 10-3 cm-1. Simultaneously the accuracy of the line positions is better than 10-5 cm-1. These extreme accuracies are needed especially in creating a set of reliable IR-line frequency standards to be used to calibrate other infrared devices. Therefore, it is very important to analyze all the possible sources of errors and find the best ways to eliminate them.
Dehydration Of Erythromycin Dihydrate A Microscopy-FTIR Application
M. A. Smith, R. S. Chao, M. S. Bergren, et al.
A novel application of microscopy-FTIR to monitor the dehydration of some hydrate compounds has been established, and some major instrumental parameters are identified. An application to erythromycin dihydrate indicated that the most notable spectral changes before and after dehydration are observed in the carbonyl region, particularly the lactone carbonyl band. Spectral comparison with conventional FTIR preparations, such as Nujol and KBR methods, are pre-sented to demonstrate the dehydration mechanism of erythromycin dihydrate. Also presented are the differential scanning calorimetry (DSC) and hot stage microscope (HSM) data to support the hypothesis that the FTIR-microscope accessory induces a transformation of erythromycin dihydrate into a metastable anhydrate form which will rehydrate rapidly when water vapor is present. With further thermal treatment the metastable form would convert to a stable anhydrate form via an amorphous form.
Quantitative Infrared Spectroscopy Of Glucose In Blood Using Partial Least-Squares Analyses
Kenneth J. Ward, David M. Haaland, M. Ries Robinson, et al.
The concentration of glucose in drawn samples of human blood has been determined using attenuated total reflectance (ATR) Fourier transform infrared (FT-IR) spectroscopy and partial least-squares (PLS) multivariate calibration. A twelve sample calibration set over the physiological glucose range of 50-400 mg/deciliter (dl) resulted in an average error of 5.24 mg/dl. These results were obtained using cross validated PLS calibration for all data in the frequency range of 950-1200 cm-1. These results are a dramatic improvement relative to those obtained by previous studies of this system using univariate peak height analyses.
A Low Temperature Infrared Study Of Deuterated NH4VO3
D. de Waal, A. M. Heyns
The existence of (NH4)2V6016 as an intermediate in the thermal decomposition of NH4V03 to V205 has been confirmed by vibrational spectroscopy, resulting in the following reaction in an open systeml: NH4VO3 1 bar, air, 50-200°C/(1) (NH4)2v6o16 1 bar, air, ca.360°C/(2) V205 The kinetics of reaction (1) was studied by means of Raman spectroscopy, and structural information on NH4V03 and (N114)V60 16 was required to obtain an accurate description of the reaction mechanism2. Information on the site symmetry of an ammonium ion and hydrogen bonding in a crystal can be obtained by considering the infrared spectra of isotopically dilute NH3D+ ions in the lattice at liquid nitrogen temperatures3, especially as the position of hydrogen atoms in (NHO2V6016 could not be determined by X-ray methods.
Analysis Of Environmental Air Sample Extracts By Gas Chromatography/Matrix Isolation-Infrared Spectrometry
Jeffrey W. Childers, Nancy K. Wilson, Ruth K. Barbour
Efforts in our laboratory are focused on developing chromatographic and spectroscopic methods for analyzing semivolatile organic compounds in air. As part of our research effort we are currently investigating the capabilities of gas chromatography/matrix isolation-infrared (GC/MI-IR) spectrometry l for characterizing air sample extracts. We have applied GC/MI-IR spectrometry to the identification of polycyclic , aromatic hydrocarbons (PAHs) in urban air particulate matter, semivolatile organic compounds in woodsmoke-impacted air, and potential indoor air irritants in new carpet.
FTIR Microspectrometry Of Individual Petroleum Fluid Inclusions In Geological Samples
M. R. O'Grady, C. M. Conroy, L. T. Taylor, et al.
The spectrum of a petroleum fluid inclusion, obtained from a producing oil well in the Gulf of Mexico, was compared with spectra obtained on three bulk oil samples produced from the same well. Comparison of the spectra of bulk and included petroleum samples shows several major differences. These differences are consistent with the loss of the more volatile components from the bulk oil samples.
Spectral Measurements Of Atmospheric OH And O2 NIR Airglow With A Michelson Fts And InGaAs Detector
Ronald Huppi, Joseph Kristl, Thomas Hudson IV
Recent developments and the integration of an InGaAs detector with a precision, compact Michelson interferometer have provided a very sensitive, reliable, and portable measurement tool for studying near infrared upper atmospheric emissions. Spectrically resolved and calibrated line intensity measurements of major portions of the Δν = 2 and the Δν = 3 band sequences of the OH Meinel airglow emissions are obtainable from ground based sites. Typically, the spectrometer provides signal-to-noise ratios of 50/1 in one minute measurement time. Time resolved rotational OH temperatures and therefore ambient temperatures corresponding to the 80 to 95 Km OH emission region can be obtained from the data. Also the metastable excited state (alAg) of the molecular 02 (0,0) band at 1.27 pm and the (0,1) band at 1.58 pm are measurable. It is even possible to observe the OH and 02 emissions during the twilight corresponding to sun illuminated conditions at the emission altitudes if spectral discrimination and background suppression techniques are applied to reduce the unwanted effects of scattered solar radiation. Thus, continuous measurements of the emissions can be performed during the daytime to nighttime transition and throughout the night.
Laboratory Scale Reaction Monitoring Using An Ftir Deep Immersion Probe
Walter M. Doyle
The Deep Immersion Probe can be coupled to most FTIR spectrometers to provide continuous in-situ monitoring of chemical composition. This paper outlines the design of a laboratory scale probe and provides an illustration of its use in monitoring the progress of an esterification reaction.
Instrumental Considerations In Infrared Biospectroscopy
James O. Alben, Craig F. Heman, John J. Hill
The 1959 cm-1 KBr impurity absorption in beamsplitters provides a convenient measurement of instability that may be used in conjunction with interferogram fluctuations to assess the total instrumental instability. Analysis of interferogram fluctuations led to environmental controls which reduced the KBr impurity band contribution in a ratioed spectrum to less than 0.9%, and facilitated measurement of sub-milliabsorbance infrared bands.
Aqueous Reversed-Phase HPLC/FT-IR Using Diffuse Reflectance Detections
V. F. Kalasinsky, T. H. Pai, R. C. Kenton, et al.
Solvent-elimination HPLC/FT-IR has become a viable combination of two important techniques, and we have been developing a system which is adaptable to both normal and reversed-phase liquid chromatography. The interface involves the deposition of HPLC eluites onto a KCI-laden train with subsequent analysis via diffuse reflectance spectroscopy, and with minor modifications, the system can be used with microbore and analytical columns. With aqueous solvents, the water is converted to methanol and acetone in a post-column reaction with 2,2-dimethoxypropane before the eluites are deposited. A number of different samples have been used to demonstrate the interface and its flexibility. Steroids, analgesics, and other pharmaceutical preparations have been separated with reverse-phase solvents and identified by their infrared spectra. For some of the compounds studied, different infrared spectra of a given compound have been found to exhibit intensity variations, which arise from different crystalline states. The differences can be concentration dependent and may be useful in obtaining semi-quantitative information from the infrared spectra. Applications involving both gradient elution and isocratic separations have been successful. The former provides the same advantages for HPLC/FT-IR as one finds in conventional HPLC. More recent work has been applied to the use of buffers such as those frequently used in bioanalytical separations. In trying to simplify the post-column reaction with water, we have immobilized dehydration reagents onto silica particles and packed these materials into a column which is inserted in-line after the analytical column. Of the reagents utilized to date, 3,3-dimethoxypropyltrimethoxysilane has been found to perform most efficiently. It has advantages over the simpler reagents because it can be regenerated in the reaction column. Results and the efficiency of the dehydration process and its relation to the type of reagent and its coverage will be discussed.
High Resolution Fourier Transform Spectroscopy Of N2O Discharge By Selective Polarization Modulation
Mohammed Elhanine, Robert Farrenq, Guy Guelachvili
A new method for the selective detection of paramagnetic molecules in high resolution Fourier spectroscopy is described. Essentially, it is founded on the circular polarization property of the Zeeman transitions in a longitudinal magnetic field. It is applied to the selective detection of the NO radical created in a N20 electrical discharge.
F.T.Spectroscopy Of OH Produced In A Microwave Surface Plasma
A. Benidar, C. Chackerian Jr., P. Chollet, et al.
Emission spectra of the hydroxyl radical have been recorded between 450 and 4200 cm-1 at 2.7 10-3 cm-1 unapodized resolution from an air+oxygen+water vapor plasma, using a surface microwave discharge. The characteristics of the source are described. The emission spectra were recorded with the F.T. spectrometer using a GeCu detector and KC1 beam splitter. One obtains pure rotational and rovibrational lines of OH in the same spectrum. High J values were observed both for the pure rotational transition in v=0 and v=1 vibrational levels, and for the rovibrational transition in the 0<-1 and 1<-2 bands. The set of line intensity data will be used to compute the electric dipole moment function of OH.
Improved Versatility Of The Connes-Type Interferometer Of Laboratoire D'infrarouge.
Q. L. Kou, J. Collet, G. Guelachvili, et al.
This article presents a new experimental set-up for automatic change of the spectral domain of our high-information interferometer. The working principle and the original optical adjustments of the system for automatically changing the beam splitters are described. This system has been installed in the interferometer and its efficiency has been actually tested during the recording of spectra. An automatic change of detectors has also been designed. A computer HP9000/350 is used to perform the Fourier transform of the interferograms and to process the spectra. This new experimental set-up makes possible to record interferograms from spectra anywhere between visible and far-IR.
Resolution, Apodisation And Bandshape In FTIR Spectrbscopy
Philip B Tooke, Stewart F Parker
The effects of finite resolution and different apodisation functions on synthetic Lorentzian bands have been investigated. (The apodisation functions chosen were those commonly available on commercial FTIR spectrometers). The effects are dramatic, the ratio of resolution/(true bandwidth) required to obtain less than 10% distortion (as judged by the peak height and width) in the band varied from 1 for boxcar to less than 0.2 for Norton-Beer (strong). A comparison of calculated and experimental results gave good agreement for the 1216 cm -1cm band of chloroform in deuterochloroform.
Diffuse Reflectance Fourier Transform Infrared Spectroscopy Of Polymers
Jan Jansen
Fourier transform infrared spectroscopy using diffuse reflectance optics (DRIFT) can be used as a quick, non-destructive and direct technique for the characterization of polymeric materials and products. The spectra obtained do not appear as normal infrared spectra because of specular and diffuse Fresnel reflections. The bands are distorted with first-derivative-like appearance. Mathematical differentiation results in characteristic high-resolution second-derivative-like spectra which are suitable for interpretation. The DRIFT technique is capable of analysing surface related phenomena and structural information is provided of polymer layers up to nanometer level thickness. Molecular orientation of polymeric materials can be characterized without using a polarizer.
Infrared Spectroscopy And The Art Of Restoration
Stephen Firth
There are many museums and art galleries in the world devoted to the preservation of paintings, sculptures and articles of cultural importance. In some cases the preservation of the museum itself as an architectural inheritance is equally important. Infrared Spectrometry is a powerful tool in the fight to prevent the decay of many works of art. Infrared Spectroscopy can be used to identify many important constituents of the original paints and then used to test the new products used for restoration. Another example is measuring the depth of penetration of preservatives in various materials. For example, building materials can be sectioned to give 30 micron slices that can be subsequently examined by transmission infrared microscopy. This yields information on the types of material present but also on the penetration depth of various preservatives.
Diffuse Reflectance On Photoacoustic Spectrometry?
Stephen Firth
Infrared Spectrometry is a powerful technique for the analysis of many types of solid samples. Diffuse Reflectance and Photoacoustic infrared sampling accessories can be used to analyse solid samples with little or no sample preparation. A comparison is made between these complementary techniques to show how they can both be used in the modern laboratory. The relative merits of each technique will be discussed and examples of the uses of the two techniques given. Particular attention will be given to the analysis of foodstuffs.
The Role Of FT-IR In The Identification Of Domoic Acid, A New Shellfish Toxin
Michael Falk
A brief but serious outbreak of poisoning by mussels occurred in Canada in December 1987. In a round-the-clock effort, the toxin that caused this outbreak was isolated in our laboratory and identified as domoic acid, a naturally-occurring substance that had not previously been reported to cause human poisoning. The identification of the toxin was achieved by the concerted use of spectroscopic methods, among them micro-FT-IR spectroscopy. The use of the FT-IR microscope allowed high-quality infrared spectra to be obtained on sub-microgram quantities of the early isolates of the toxin. The microscopic method had an additional advantage in that it enabled us to carry out a rough but rapid separation of the compound of interest from admixtures of unrelated substances by recording the spectra of a gradually dried out drop of solution on a microscope plate. Following the positive identification of the toxin as domoic acid, a detailed spectroscopic study was made of this important molecule in its several isomeric forms.
FTIR Monitoring Of Polyisoimide Transformation
Morris J. Weiss
Increasing Use Of Isoimide Technology In Polyimide Processing Has Warranted Additional Application Of Analytical Techniques To Assay Concentration Of Polyisoimide Precursors Which Can Be Thermally Isomerized To Their Respective Polyimides Without Loss Of Volatiles. A Method Is Described Of Characterizing And Standardizing The Optimum Cure Temperature For A Given Polymer Blend By Plotting The Ratio Of The Characteristic Ir Bands For The Representative Of The Isoimide And Imide Configurations. Ftir Spectroscopy Is Used To Monitor The Extent Of Isomerization For A Number Of Polymer Blends And Mixtures Of Pbi (Polybenzimidazole) And A Polyisoimide Oligomer.
Radiometric Calibration Of Fourier Transform Semiconductor Photoluminescence
N. L. Rowell
The radiometic calibration of a Fourier transform spectrometer has been carried out with relation to semiconductor photoluminescence. The technique employed made use of a calibrated source of spectral irradiance and a diffuse reflector of known spectral reflectance. To obtain the instrumental calibration from 700 meV to 1500 meV (5600 to 12000 cm-1), the luminescent material was replaced by the illuminated diffuser and its spectrum was measured. An example is given of the photoluminescence of a silicon film grown by molecular beam epitaxy (MBE) with in situa ion beam doping (IBD) of Ask+-ions. The spectra before and after the application of the radiometric correction are compared over the range 740 to 1160 meV.