Multivariate calibration applied to the quantitative analysis of infrared spectra
Author(s):
David M. Haaland
Show Abstract
Multivariate calibration methods are very useful for improving the precision, accuracy, and reliability of quantitative spectral analyses. Spectroscopists can more effectively use these sophisticated statistical tools if they have a qualitative understanding of the techniques involved. A qualitative picture of the factor analysis multivariate calibration methods of partial least squares (PLS) and principal component regression (PCR) is presented using infrared calibrations based upon spectra of phosphosilicate glass thin films on silicon wafers. Comparisons of the relative prediction abilities of four different multivariate calibration methods are given based on Monte Carlo simulations of spectral calibration and prediction data. The success of multivariate spectral calibrations is demonstrated for several quantitative infrared studies. The infrared absorption and emission spectra of thin-film dielectrics used in the manufacture of microelectronic devices demonstrate rapid, nondestructive at-line and in- situ analyses using PLS calibrations. Finally, the application of multivariate spectral calibrations to reagentless analysis of blood is presented. We have found that the determination of glucose in whole blood taken from diabetics can be precisely monitored from the PLS calibration of either mid- or near-infrared spectra of the blood. Progress toward the noninvasive determination of glucose levels in diabetics is an ultimate goal of this research.
Understanding spectra of highly excited vibrational states
Author(s):
Ian M. Mills
Show Abstract
Some of the characteristics of high overtone spectra observed in the near infrared are discussed, particularly in relation to local mode effects, the increasing density of states, and the effect of inter-state resonances and intramolecular vibrational redistribution.
FTIR spectroscopy, site-directed mutagenesis, and isotope labeling: a new approach for studying membrane proteins
Author(s):
Yi-Wu He;
Mark P. Krebs;
Judy Herzfeld;
H. Gobind Khorana;
Kenneth J. Rothschild
Show Abstract
The FTIR absorption spectrum of a membrane protein contains bands due to the vibrations of individual chemical groups. Site-directed mutagenesis can be used to assign such bands to individual amino acid residues. Using this method, a band from the amino acid residue Tyr- 185 of bacteriorhodopsin, a light-driven proton pump, was identified in the low temperature FTIR absorption spectrum. Its intensity and frequency indicate that Tyr-185 exists in a partially deprotonated form in light-adapted bacteriorhodopsin.
Vibrational polaritons in thin semiconducting films on metal surfaces
Author(s):
Evgenyi A. Vinogradov
Show Abstract
Optical properties of thin films of poiar dielectrics and semiconductors were the subject of a great number of scientific and technical publications. However, during the last twenty years new experimental results have been obtained which enriched our notions about the interaction of electromagnetic radiation with the condensed state of a substance. The most important of them are: -detection of radiative surface polaritone in thin crystalline films of polar semiconductors 12; detection of strong interaction between elementary excitations in adjacent media (a film and a substrate) 35; detection of Raman scattering at the frequencies of wave-guide "and of interference polari tons; observation of the spectra of thermostimulated radiation, absorption, luminescence and resonance Raman scattering (RRS) at the frequencies of interference modes (IMs) in filn -detection of strong resonance interaction between local vibrations of impurity atoms and IMs in films In the present paper an attempt is made to explain the totality of the experimental data the author is aware of on optical properties of the ifims of different thicknesses from super thin to bulk single crystals obtained by various optical spectroscopy methods within the framework of macroscopic linear crystal optics in the polariton language.
Near-infrared spectroscopy: the new FT frontier--spectroscopic and chemometric considerations
Author(s):
Edward Stark
Show Abstract
Several orthogonal calibration sets of aliphatic and aromatic hydrocarbon mixtures have been designed to explore the effects of spectral resolution, spectral information within a spectral range, wavenumber imprecision and scale shifts, dynamic range, and noise on the chemometrically derived quantitative calibrations for hydrocarbon mixtures. The first two of these parameters have been studied on six very similar aromatic compounds in this, the first of a series of studies which also include aliphatic straight chain, branched, unsaturated, and cyclic compounds. The 6000 to 9500 cm-1 near-infrared derived chemometric calibration accuracy, as compared to gravimetric values, ranged from less than 0.04% to 0.2% error for each of the six components in the mixtures.
In-situ investigation of activated zeolites by diffuse-reflectance FTIR spectroscopy
Author(s):
Reiner Salzer
Show Abstract
A new sample stage with minimal thermal expansion was used to investigate the activation process of zeolites. The results were displayed quasi-continuously by mapping the reflectance changes across the investigated spectral range. Such contour plots provide a more detailed insight into the sample behavior than individual difference spectra do. Long-term investigations were performed in the mid-infrared on glass-sealed activated samples. The solid state ion exchange between ZnO and H-ZSM-5 zeolite was studied at 450 degree(s)C. In erionites, the relation between the desorption of different ammonia species and the formation of OH groups during the activation has been studied up to 600 degree(s)C. The diffusion of water and the formation of hydroxonium ions was observed. In activated Y zeolite the intercrystalline diffusion of protons has been analyzed.
Investigation on impurity behavior in semiconductors by use of Fourier transform spectroscopy
Author(s):
Shue-Chu Chen
Show Abstract
We report the comprehensive results obtained in our group in the investigation of impurity behavior in semiconductors by use of Fourier transform spectroscopy. We put emphasis in this paper on the electronic transitions of shallow impurities in ultrapure silicon. The new results reported here include the discovery and investigation of new shallow centers, the photothermal ionization spectroscopy of phosphorus in Si under high magnetic field, and the high sensitivity and resolution of PTIS as used for detection of shallow impurities in ultrapure silicon.
Quantitative evaluation of molecular orientation in thin Langmuir-Blodgett films by FTIR spectroscopy and its application to the study of structure-function relationship
Author(s):
Tohru Takenaka;
Junzo Umemura;
T. Kawai;
Toshihide Kamata;
Naokazu Koizumi
Show Abstract
A method for quantitative evaluation of the molecular orientation in thin Langmuir-Blodgett (LB) films by FT-IR transmission and reflection-absorption (RA) spectroscopy is presented and applied to the study of the 11-monolayer LB film of barium salt of an azobenzene- containing long-chain fatty acid. This was also applied to the study of temperature dependence of the molecular orientation in alternate LB films consisting of a phenylpyrazine-containing long-chain fatty acid and deuterated stearic acid as well as in those consisting of their barium salts. At the same time, pyroelectricities of these films were measured in the temperature range from -30 to 60 degree(s)C, and the results were discussed in connection with changes in the molecular structure and orientation.
Raman: FT or dispersive--is that the question?
Author(s):
Bernhard D. Schrader;
Stefan Keller
Show Abstract
The typical properties of the Raman spectrometers for the near-infrared range are discussed. Multiple monochromators, polychromators, and interferometers have specific advantages and disadvantages. They complement each other nicely.
FTIR, bushfires, and atmospheric chemistry
Author(s):
David W.T. Griffith
Show Abstract
Biomass burning makes an important impact on atmospheric chemistry through the emission of large quantities of many trace gases into the atmosphere. We describe the application of three FTIR-based methods to the analysis of the composition of the smoke from different types of biomass fires. In two laboratory-based methods, smoke samples are analyzed by gas-phase absorption and matrix isolation FTIR spectroscopy. In the third method, an FTIR spectrometer is used in the field to measure absorption spectra in situ in the plumes from prescribed and large scale laboratory fires.
FTIR spectroscopy of layered structures: thin solid films, coated substrates, profiles, multilayers
Author(s):
Peter Grosse
Show Abstract
Thin solid films and surfaces are characterized by FTIR-spectroscopy, based on reflectance and transmittance measurements, in particular with polarized light at oblique incidence. Thus two independent data sets for s- and ppolarization are available. At p-polarization additional absorption lines at the zeros of the dielectric function are observed (Berreman-effect). The interpretation of the measured spectra is carried out by the following procedure: the observed reflectance and transmittance are simulated by spectra, calculated from a model by an optimum fit of the model parameters. As a result the specimens are characterized in terms of vibronic resonances, contribution of free electrons and holes, thicknesses of the various layers in a stack, and of profiles of chemical composition. Thicknesses and roughness of very thin layers are determined from measurements of the reflectance of X-rays at grazing incidence. The interpretation is also based on model simulations. In detail the following examples are discusses: thin Ag-films deposited on glass, oxide films on semiconductors and metals, depth depending profiles ofextrinsic atoms due to diffusion or ion implantation, and semiconducting multilayer structures. The reliability of the non-destructive IR-method is compared with other relevant analytic methods as SIMS, RBS, and AES.
Localized vibrations: moles in structure-land
Author(s):
John H. van der Maas
Show Abstract
Functional groups reveal specific information about their direct surroundings; in fact, they form the moles, the undercover agents, in molecules. However, as with agents, the information is produced in coded form (spectral data) so one has to know the code in detail before the message is completely understood. The substantially improved accuracy (wavenumber, intensity) and sensitivity brought about by FT-instruments, in combination with computer software, offer extended spectral information. Functional groups can now be examined in great detail. Obviously the amount of deducible structural items is group dependent, implying that one has to pursue the probing qualities of a functionality prior to use. The OH-group, and more in particular the OH-stretching vibration, proves to be an extremely good mole. Its potentials are demonstrated on conformational studies of various saturated alcohols, the presence of OH(DOT)(DOT)(DOT)(pi) bridges, the strength and type of OH(DOT)(DOT)(DOT)O bridges, all in an apolar solvent, and on the disclosure of different hydrogen bonds in some solid samples.
Transition moments in optical spectroscopy
Author(s):
Erik W. Thulstrup
Show Abstract
Electronic and vibrational transitions are characterized not only by energy and intensity, but also by direction. The measurement of transition moment directions in absorption is often experimentally simple and may provide essential information for assignment and recognition of transitions. It may also be used for determination of molecular alignment, structure, and conformation. Two-photon processes, such as luminescence, may provide even more detailed information of this kind. Applications of the techniques are found areas like materials science, microelectronics, and biochemistry and physics. The experimental determination of moment directions is frequently based on production of aligned samples, either by photoselection or by the use of anisotropic solvents, such as liquid crystals or stretched polymers. Two examples from absorption spectroscopy are used to illustrate the wide applicability of a simple, but frequently overlooked, experimental technique, as well as methods for interpretation of the spectra.
FTIR of polymers: a 15-year perspective
Author(s):
Jack L. Koenig
Show Abstract
Originally, JR spectra of polymers were measured using a dispersive instrument
equipped with an optical element of prisms or gratings to geometrically disperse
the infrared radiation'. Using a scanning mechanism, the dispersed
radiation is passed over a slit system which isolates the frequency range
falling on the detector. In this manner, the spectrum, that is, the energy
transmitted through a sample as a function of frequency is obtained. This
dispersive JR method is highly limited in sensitivity because most of the
available energy is being thrown away , i. e• , it does not fall on the open
slits and hence does not reach the detector. To improve the sensitivity of
JR, a multiplex optical device was sought which allows the continuous detection
of all of the transmitted energy simultaneously. The Michelson interferometer
is such an optical device and the JR instrumentation which resulted
is termed an Fourier Transform infrared (FT-JR) spectrometer2 The Fourier
transform process was well known to Michelson and his peers, but the computational
difficulty of making the transformation prevented the application of
this powerful technique to spectroscopy. An important advance was made with
the discovery of the fast Fourier transform (FFT) algorithm by Cooley and
Tukey3 which breathed new life into the field of spectroscopy using interferometers
by allowing the calculation of the Fourier transform to be
carried out rapidly. As computers have improved, the time required for a
Fourier transform has been reduced to such an extent that the spectra can be
calculated during the time needed for the moving mirror to return to its
starting position.
When we acquired our first FT-JR instrument, we were impressed with the
performance and depressed by the lack of software to manipulate the spectra.
Since the infrared spectral data from FT-JR are recorded in digital form, a
variety of digital data processing techniques are available to eliminate
spectral distortions. These distortions can arise from such things as sample
scattering and reflection or from sampling devices such as ATR, photoacoustic,
and diffuse reflection. The digital data processing techniques are also used
to isolate spectral features for study and quantification.
Kinetics of catalyzed processes studied by FTIR spectroscopy
Author(s):
Johannes A. Lercher
Show Abstract
The role of IR spectroscopy to characterize the surface of solid catalysts and to evaluate important intermediates of catalyzed reactions is outlined and documented with case studies. The instrumentation requires the capability to record IR spectra in situ at elevated temperatures and pressures as well as the possibility to confine precisely the volume of analysis. It is shown that FTIR spectroscopy can significantly contribute to the understanding of industrially used catalyzed processes and to the development of new catalysts.
Fourier transform spectroscopy for high-Tc superconductors
Author(s):
Ludwig Genzel
Show Abstract
Far-infrared spectroscopy was one of the important experimental techniques for the investigation of classical superconductors. Not long after the clear prediction of an excitation energy gap by the BCS theory, the gaps of various superconductors could be found spectroscopically. At that time the experiments were extremely difficult, since the gap frequencies occurred in the very far infrared and because the spectroscopic techniques were not as far developed as today. Because gap frequencies (omega) g and critical temperature Tc of superconductors are directly interrelated, one should expect the gaps of the high-Tc cuprates to occur at higher frequencies in the far infrared, thus being easier to access. It turned out, however, that this is not the case by reasons which are described later. At the moment, no completely clear evidence for the positions of the gaps exists in the case of clean, undoped high-Tc superconductors, while clear evidence was found in the case of iron- doped YBa2Cu3O7-(delta ). This paper describes mainly the problems concerning the spectroscopic methods, while the superconducting properties are only briefly sketched.
Dispersive Fourier transform spectroscopy for the range 1-30cm-1
Author(s):
Derek H. Martin;
R. J. Martin;
Ya-Quan Gong;
John W. Bowen
Show Abstract
Some notable spectroscopic and radiometric investigations have been made recently using Fourier
Transform Spectrometric (FTS) techniques down to frequencies as low as 1 cm', 30 Gllz, overlap the
microwave range. There are also important applications of such techniques in the development and
proving of components for use in millimetre-wave and terahertz communications systems (for this reason
FTS is best interpreted as Fourier Transform Spectrometry, rather than Spectroscopy). Our purpose here
is to illustrate the special design and operational considerations that arise for FTS at these extreme low
frequencies.
In-situ FTIR spectroscopy at the electrochemical interface: the interest of a modulation technique
Author(s):
J. N. Chazalviel;
K. C. Mandal;
F. Ozanam
Show Abstract
Infrared vibrational spectroscopy is increasingly being used as a tool for the in situ study of the electrochemical interface. The geometry may be that of external reflection with a thin- layer-electrolyte cell, or that of internal reflection in the case of infrared-transparent (e.g., semiconducting) electrodes. The small infrared absorption from the interfacial species can be separated out from the large electrolyte absorption background by making use of its specific dependence upon electrode potential. We describe an original technique combining audio- frequency modulation of the electrode potential, together with Fourier-transform infrared spectroscopy. This technique provides an unprecedented sensitivity of (Delta) I/I approximately 10-6 under typical operating conditions. It further allows a better identification of the species under study, by using the capability of probing the dynamics, inherent to a modulation technique. This allows one to differentiate between the different mechanisms that may lead to potential dependent changes at an electrochemical interface. The technique is illustrated by several applications: study of the ionic layer, interfacial species and their relation to electronic surface states at the n-Si/acetonitrile-electrolyte interface, study of the reversible reduction of solute species at a Ge/aqueous electrolyte interface, study of the catalytic mechanism of hydrogen evolution after this interface has been irreversibly modified by reduction of heteropolyanions.
Acousto-optic tunable filter NIR spectrometer for rapid process-control
Author(s):
M. Huehne;
U. Eschenauer;
Heinz W. Siesler
Show Abstract
The performance of a near-infrared spectrometer equipped with light-fiber optics and an acousto-optic tunable filter (AOTF) instead of the conventional grating-monochromator or interferometer is described. The spectrometer is used for quantitative on-line analyses with the help of chemometrics.
Finite resolution and apodization in FT-Raman spectra
Author(s):
Philip B. Tooke;
V. Patel;
K. P.J. Williams;
Stewart F. Parker
Show Abstract
The effects that finite resolution and choice of apodisation function have on Fourier transform (FT) Raman spectra are illustrated by the 839 cm-1 ((nu) 1) and 914 cm-1 ((nu) 3) bands of KMnO4. FT-Raman spectra were recorded at 0.5, 2, 4, 8, and 16 cm-1 resolution using boxcar, Norton-Beer (medium) and triangular apodisation functions at each resolution. The results show that the dramatic changes in bandshape that occur as the ratio (resolution/true full width at half height of band) increases is strongly dependent on the choice of the apodisation function.
Efficient method for optical constant determination by FTIR-ATR
Author(s):
Koji Ohta;
Hatsuo Ishida
Show Abstract
We propose a novel iterative method to obtain optical constant spectra in the infrared region from FT-IR/ATR spectra. The algorithm consists of three steps. The first step is to obtain a trial extinction coefficient spectrum k(v) from a measured ATR spectrum, using the assumption that the two spectra are proportional to each other. The second step is the Kramers-Kronig (KK) transformation for obtaining the refractive index spectrum n(v) from the k(v) spectrum. The last step is a refining process of the k(v) spectrum using the calculated n(v) spectrum and the measured ATR spectrum. The last two steps are repeated until n(v) and k(v) spectra are stable. The present method adopts the most efficient algorithm at each step of the iteration. The rate of convergence of the iteration depends on the measurement conditions for the ATR spectrum and the maximum k(v) value. The use of germanium as a material for the internal reflection element (IRE), and 45 degrees as the incident angle, is found to give good convergence for the range of the k(v) values of most organic materials. This method is applied to several polymer films directly cast on the IRE prism from solution. The results are in good agreement with those obtained with other methods using transmission spectra.
High-pressure liquid cell for use in the near- and mid-infrared regions
Author(s):
A. Idrissi;
M. Arroume;
George C. Turrell
Show Abstract
With recent developments in infrared and Raman instrumentation, it is now feasible to make quantitative measurements of vibrational band profiles as functions of pressure. In Raman spectroscopy the design of liquid cells for moderate pressures is relatively easy. However, in infrared spectroscopy the problem is more difficult, primarily because of the lack of suitable window materials. This paper describes a cell which was developed in the laboratory for high- pressure work, in particular for the study of the infrared spectra of small molecules such as HCl and DCl in inert solvents.
Fourier transform infrared dichroism investigation of molecular orientation in model networks of poly(dimethylsiloxane)
Author(s):
S. Besbes;
L. Bokobza;
L. Monnerie
Show Abstract
Segmental orientation in model networks of poly(dimethylsiloxane) PDMS in uniaxial tension are measured by infrared dichroism. Measurements are made on four tetrafunctional end- linked networks having molecular weights of 2000, 5000, 10,000, and 23,000 between junctions. The orientational function is shown to increase with cross-linking density. In the case of swollen samples, the orientational order parameter is found to increase with the degree of swelling. For a bimodal system consisting of two different molecular-weight species, the two types of chains tend to present the same orientational behavior.
ATR-FTIR investigations of plasticizer diffusion in polymers
Author(s):
C. S. Miser;
Kevin L. McNesby;
Rose A. Pesce-Rodriguez;
Robert A. Fifer
Show Abstract
An attenuated total reflectance FTIR (ATR-FTIR) technique has been developed for measuring the diffusion coefficients of liquids in polymer films. Data is being obtained for diffusion of plasticizers in nitrocellulose (NC), cellulose acetate butyrate (CAB), and NC/CAB mixtures.
Characterization of plasticizers in solid propellant formulations by FTIR-microscopic, FTIR-photoacoustic, and GC-FTIR techniques
Author(s):
Rose A. Pesce-Rodriguez;
Robert A. Fifer
Show Abstract
Investigation of plasticizer levels in solid propellants has been carried out using three FTIR techniques: FTIR-microscopy (FTIR-mic), photoacoustic-FTIR (PA-FTIR), and gas chromatography-FTIR (GC-FTIR). Two plasticizers have been examined; only one of these appears to have a tendency to evaporate from the solid propellants. It was observed that when both plasticizers are present in the same formulation, evaporation of the more volatile plasticizer is notably decreased. Significantly higher levels of plasticizer and polymeric binder have been found at extruded surfaces than have been found in the interior of the grain. Desorption-GC-FTIR analysis revealed a relationship between processing conditions and residual solvent content.
Testing and development of a mobile Fourier transform infrared spectrometer system for the analysis of atmospheric pollutants
Author(s):
Mark R. Witkowski;
Charles T. Chaffin Jr.;
Timothy L. Marshall;
Martin L. Spartz;
Jonathan H. Fateley;
Robert M. Hammaker;
William G. Fateley;
Ray E. Carter Jr.;
Dennis D. Lane;
Glen A. Marotz;
Billy J. Fairless;
Jody L. Hudson;
Joseph Arello;
Mark J. Thomas;
D. F. Gurka
Show Abstract
The mobile Fourier transform infrared (FT-IR) spectrometer system for the monitoring of volatile organic compounds (VOCs) is now entering its third and final stage of testing. At present, data have been collected in all three stages of testing. From the results obtained during the three stages of testing, modifications have been made to the mobile FT-IR spectrometer system to increase its overall performance in the field.
Identification of photolysis products of chloro-nitrobenzenes by means of cryotrapping GC-FTIR
Author(s):
Marjo J. Vredenbregt;
H. A. den Hollander;
Tom Visser
Show Abstract
Structural analysis of the photochemical reaction products of ortho, meta, and para chloro- nitrobenzene in demineralized and humidic aqueous solution has been carried out. In addition to GC/MS, cryotrapping GC/FTIR has been used for isomer differentiation and identification. Fifteen metabolites have been identified including 10 chloro-nitrophenol isomers.
Study on the hydration of poly(vinyl acetate) by FTIR spectroscopy
Author(s):
Ruigang Yao;
Duan-Fu Xu;
Qiang Li;
Shifu Weng;
Yongnian Yang;
Zhen-hua Xu;
JinGuang Wu;
Guang-Xian Xu
Show Abstract
For hydrated poly(vinyl acetate) (PVAc), a series of Fourier-transform infrared (FTIR) spectra were obtained by the subtraction procedure. The relationship between the integral intensity of the O-H stretching bands in the spectra and water contents showed that water molecules absorbed in PVAc associate with each other gradually to form isolated clusters and/or microdomains as the value of water contents reached 1.40 weight percent. Significantly, not only the peak positions and absorbances of relating bands (such as C equals 0, C-O, O-CH) with ester group, but also those of C-H bands in PVAc were affected by the hydration.
Application of a knowledge-based system for the automated characterization of copolymers from infrared spectral data
Author(s):
J. A. de Koeijer;
Hendrik J. Luinge;
John H. van der Maas;
Paul Tayler;
John M. Chalmers
Show Abstract
The development of a knowledge-based system for the characterization of aromatic polymers is described. Spectrum-structure correlations are deduced automatically from DRIFT and ATR spectra of homopolymers. Using these correlations spectra of copolymers and blends are interpreted yielding qualitative information on the monomer composition. Band ratio analysis and partial least squares regression are applied to characterize the samples quantitatively.
Spectral and kinetic investigations of chirally deuterated three-membered ring molecules using Fourier transform vibrational-circular-dichroism spectroscopy
Author(s):
Teresa B. Freedman;
N. Ragunathan;
S. J. Cianciosi;
J. E. Baldwin;
Laurence A. Nafie;
J. A. Moore;
J. M. Schwab
Show Abstract
Vibrational circular dichroism (VCD) and kinetic measurements have been carried out for several three-membered ring molecules that are optically active by virtue of isotopic substitution, (S,S)-cyclopropane-1,2-2H2, (2S,3S)-cyclopropane-1- 13C,2H-2,3-2H2, and (S,S)-oxirane-2,3-2H2.
Fourier transform vibrational-circular-dichroism studies of model peptide molecules
Author(s):
Mario J. Citra;
M. Germana Paterlini;
Teresa B. Freedman;
Laurence A. Nafie;
A. Shanzer;
Y. Tor;
Claudio Pratesi;
Osvaldo Pieroni
Show Abstract
Vibrational circular dichroism (VCD) spectra have been recorded in the NH and C equals O stretching regions for a series of tripodal peptides and peptides containing an unsaturated residue, in order to obtain information about solution conformations.
Spectroscopic infrared ellipsometry
Author(s):
A. Roseler
Show Abstract
The spectroscopic infrared ellipsometry (SIRE) by means of the combination of a photometric ellipsometer with a Fourier transform spectrometer is used to measure optical properties in the infrared. From the observed four Stokes parameters, the spectrum of the degree of polarization after the reflection at the sample is calculated and discussed.
Near-infrared spectroscopy of Martian surface by the ISM experiment
Author(s):
Gabriele Arnold;
Alexei Grigoriev
Show Abstract
Near-infrared reflectance spectra of the Martian surface taken from the imaging spectrometer ISM have been analyzed to study the composition of the surface. The most prominent spectral criteria related to the surface are found to be variations of infrared brightness, of continuums slope, of absorption features between 2.2 and 2.5 micrometers , of a band of bound water at 3 micrometers and of the complex ferric-ferrous absorption near 1 micrometers . Spectral maps created from the ISM data allow us to discuss variations of composition and surface morphology.
Novel asynchronous time-resolved Fourier transform IR spectroscopy
Author(s):
Koji Masutani;
Akira Yokota;
Yukio Furukawa;
Mitsuo Tasumi
Show Abstract
We have developed a novel asynchronous time-resolved FT-IR spectrophotometer based on a conventional continuous-scan interferometer. In contrast to the existing methods, this new method does not require the synchronization between the signal for time resolving and that for the sampling of the A/D converter. The naming of the `asynchronous time-resolved' comes from this feature
Far-infrared reflectance and ellipsometric studies of GaAs-AlAs superlattices
Author(s):
E. Jahne;
A. Roseler;
Klaus H. Ploog
Show Abstract
The most popular semiconductor superlattices (SL's) grown and investigated up to now are the GaAs—AlAs SL's. With regard to its infrared resp onse it is useful to treat the SL as a single uniaxial medium with e as in-plane component and e as out-of-plane component of the dielectric function tensor (the zdirectionis the growth direction of the SL). In a normal-incidence reflectivity experiment only is probed. To study and by it the layeringintroduced anisotropy it becomes necessary to use oblique incidence as it provides an electric field component normal to the SL surface as well as one parallel to it. There are reports using DFTS,' oblique incidence power reflection spectroscopy with polarized light,2 and ATR spectroscopy.3 As a very powerful method for such studies seems to be variable angle spectroscopic ellipsometry (VASE).4 It measures both the ratio of the amplitudes of p and s polarized reflected light and the cosine of the phase shift between p and s polarized reflected light, denoted usually by tan b and cos respectively.
Oxygen precipitate mapping in silicon using micro-FTIR spectroscopy
Author(s):
Adele Sassella;
Alessandro Borghesi
Show Abstract
We present a new high spatial resolution Fourier transform infrared technique which can detect low concentrations of SiO2 particles embedded in a silicon matrix. We use 30 micrometers diameter spots and scan the samples to obtain an optical response map of such precipitates.
Time-resolved FTIR studies on proteins
Author(s):
Georg Souvignier;
Klaus Gerwert
Show Abstract
Two different time-resolved FTIR techniques are used to investigate the light-driven proton pump bacteriorhodopsin: (1) the rapid scan technique yielding a few ms time-resolution, and (2) the stroboscopic technique yielding a few microsecond(s) time-resolution.
Oxygen impurities in epitaxial silicon grown on Czochralski substrates: recent advances by micro-FTIR spectroscopy
Author(s):
M. Geddo;
B. Pivac;
Angiolino Stella
Show Abstract
The interstitial oxygen profile across the epitaxial silicon and Czochralski silicon interface has been determined using a micro Fourier transform infrared technique. Systematic measurements performed in transversal wafer cross-section configuration demonstrate the presence of interstitial oxygen in the epitaxial layer, clearly indicating that solid state outdiffusion from the substrate occurs during film preparation. Moreover, it is shown that oxygen contamination may produce precipitation phenomena inside the film.
Spray-jet assembly interface for the coupling of reversed-phase narrow-bore LC and FTIR spectrometry
Author(s):
G. W. Somsen;
Cees Gooijer;
Udo A. T. Brinkman;
Nel H. Velthorst;
Tom Visser;
A. P. J. M. de Jong
Show Abstract
Reversed phase liquid chromatography (RPLC) has been coupled to Fourier transform infrared spectrometry (FTIR) via solvent elimination and effluent deposition using a spray jet assembly. The chromatographic separation is hardly affected. Identification limits are in the 10 - 20 ng range. The system can handle eluent containing up to 40% water. The usefulness of the interface in impurity profiling of steroids is demonstrated.
Vibrations of H8Si8O12, D8Si8O12, and H10Si10O15
Author(s):
M. Baertsch;
P. Bornhauser;
Gion Calzaferri
Show Abstract
We report the observed and calculated fundamental IR and Raman frequencies of H8Si8O12 and D8Si8O12. Assignments are based on normal coordinate analysis and given in terms of internal vibrations. The NIR FT-Raman spectrum of the D5h-H10Si10O15 molecule in the range 65 - 3000 cm-1 is shown.
Quantitative evaluation of conformational changes in ribonuclease A as a function of pD
Author(s):
A. Zanobi;
R. Fusco;
C. Marinensi
Show Abstract
The FT-IR spectra (Amide I band) of Ribonuclease A dissolved in D2O were analyzed. The evolution of peculiar substructures as a function of pD was quantitatively evaluated. The structural change observed at pD equals 3 was related to the cleavage of the salt bridges formed by aspartic and glutamic acids.
Absolute absorption intensities of liquids: towards the determination and use of secondary infrared absorption intensity standards; absorption intensities of liquid benzene
Author(s):
John E. Bertie;
C. Dale Keefe;
R. Norman Jones
Show Abstract
In this paper we examine the accuracy of different algorithms for the FFT-based Hilbert transform, compared with the much slower Kramers-Kronig transform. For the transform from imaginary to real refractive indices, the Kramers-Kronig transform gives deviations from the correct n((nu) ) spectra of 0.05%, while some existing algorithms for the Hilbert transform give up to 4% deviation over a wide wavenumber range. The BZ algorithm for the Hilbert transform is presented which gives n((nu) ) accurate to 0.05% deviation, the same as the Kramers-Kronig transform. The BZ algorithm for the transform from real to imaginary refractive index gives k((nu) ) accurate to 0.2% of the largest k((nu) ) value in the spectrum.
Spectroscopy of short-lived spin-polarized molecular complexes
Author(s):
Victor A. Kartoshkin;
George V. Klementiev
Show Abstract
Several quasi-bound complexes `excited atom-molecules' were shown to be spin-polarized. Due to spin-rotation interaction, molecules became rotation-polarized. This effect may be used to investigate rotational excitation of molecules and molecular ions.
FTIR characterization of epitaxial silicon layers
Author(s):
J. A. Engelbrecht;
R. L. Kleinhenz;
R. A. Bendernagel
Show Abstract
FTIR reflectance spectroscopy was employed in an attempt to nondestructively determine the thickness as well as the dopant concentration of epitaxial silicon layers in p-/p+ structures on p-substrates.
FTIR spectrometric investigation of tin-doped indium oxide coatings on quartz glasses
Author(s):
R. Kalaehne;
K. Bolick;
K.-D. Schleinitz;
M. Rottmann;
Karl Heinz Heckner;
P. Klobes
Show Abstract
FTIR spectra of tin-doped indium oxide (ITO) coatings on quartz substrates are interpreted by fitting model functions. ITO coatings are prepared by dc sputtering. The sputter gases contain O2, Ar, and CF4, CCl2F2 and CBr2F2, respectively. The measured thickness d of deposited ITO coatings on quartz glass substrates differs between 40 and 540 nm. Carrier concentration and mobility are estimated.
High-resolution Fourier transform spectrum of magnesium donors in silicon
Author(s):
Lawrence T. Ho;
F. Y. Lin;
Yi Sun
Show Abstract
The electronic excitation spectrum of magnesium donors in silicon has been investigated under the high resolution of a Fourier-transform spectrometer. Using a strain-free technique, the linewidths of the excitation lines measured at liquid helium temperature are observed to be much narrower than those reported earlier in the literature. Several new lines corresponding to excitation from ground state to higher excited states have also been observed and identified.
Automated FTIR grazing angle microscopy: a new approach to microspatial chemical mapping of thin films
Author(s):
Frederick P. Eng;
Charlene D. Shebib
Show Abstract
With the recent emergence of microscopes combined with FT-IR spectrometers, a new approach to micro-analyze polymer, organic, and inorganic materials has evolved. Samples with size and thickness less than 100 micrometers and 5 nanometers, 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. The grazing angle microscope, which is relatively 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 microscopic scale that could not possibly or easily be achieved in the past by any analytical technique. A program with different mapping patterns such as straight lines, squares, rectangles, circles, spirals, sectors, and circular bands has been developed using an IBM PC/AT that controls both the FT-IR spectrometer and the motorized X-Y-Z and theta positioning stage of the microscope.
Rheo-optical vibrational spectroscopy of polymers
Author(s):
U. Hoffmann;
M. Zahedi Azad;
N. Voelkl;
Ch. Kulinna;
S. Okretic;
Heinz W. Siesler
Show Abstract
The mechanical properties of polymeric materials are of considerable importance to their engineering applications, and the increased need for more detailed data and a better understanding of the mechanisms involved in polymer deformation has led to the search for new experimental techniques to characterize transient structural changes during mechanical processes. Simultaneous vibrational (FTIR) spectroscopic and mechanical (so-called rheo- optical) measurements have emerged as a very informative probe for the study of deformation and relaxation phenomena in polymer films in the late seventies and have since then been applied to obtain data on the orientational and conformational changes and strain-induced crystallization during the mechanical treatment of a wide variety of polymers.
Conformational equilibria and infrared matrix isolation spectra of bromoacetyl chloride and bromoacetyl bromide
Author(s):
Ashraf A. El-Bindary;
Anne Horn;
Peter Klaeboe;
Claus J. Nielsen
Show Abstract
IR spectra of the title compounds were investigated in argon and nitrogen matrices at 14 K with nozzle temperatures from 313 to 900 K. After annealing to 30 - 34 K the spectra changed considerably and the high energy conformer (gauche) nearly vanished. The matrix spectra supported the assignments into anti and gauche conformer bands, based upon bands disappearing on crystallization, and due to the small band widths various instances of overlapping bands were detected. Raman spectra were recorded as liquids at various temperatures and as amorphous and crystalline solids. The matrix spectra recorded at different nozzle temperatures gave as an average (Delta) HO (gauche - anti) equals 1.7 +/- 0.6 in bromoacetyl chloride and 2.9 +/- 0.6 kJ mol-1 in bromoacetyl bromide which are lower than in isothermal vapor cells, indicating that the high energy conformer (gauche) was partly converted to anti during deposition. The corresponding (Delta) HO values in the liquid (Raman) were 4.7 +/- 0.4 and 6.6 +/- 0.4 kJ mol-1, respectively.
FTIR studies of the reaction between atomic oxygen and CH3Br, CH2Br2, and CHBr3 in argon matrices
Author(s):
Emilie Lasson;
Peter Klaeboe;
Claus J. Nielsen
Show Abstract
The reaction of singlet atomic oxygen with CH3Br, CH2Br2, CHBr3 and CDBr3 trapped in argon matrices at 15 K have been studied by FTIR and by UV spectroscopy. CHBr3 and O(1D) reacts in the matrix to form COBr2 and HBr or HCOBr and Br2. The reaction between O(1D) and CH2Br2 in the matrix appears to lead directly to a HBr(DOT)(DOT)HBr(DOT)(DOT)CO complex while in the reaction between CH3Br and O(1D) the major product seems to be a quite photostable complex between H2CO and HBr.
Application of FTIR spectroscopy for the prediction of properties of Australian refined-petroleum products
Author(s):
Serge Kokot;
Nazaneen Asker
Show Abstract
An NIR/mid-IR approach for the prediction of properties of petroleum products such as reformate (REF), light catalytic naphtha (LCN) and stripper bottom (STRBM) is outlined. Examples of suitable spectral ranges selected with the assistance of property correlation spectra and statistics are shown and some illustrations of predictions of properties such as the research octane number (RON) and the flexible volatility index (FVI) are provided.
Application of DRIFT spectroscopy for the matching of dye extracts from small textile samples
Author(s):
Serge Kokot;
Stewart Carswell
Show Abstract
A DRIFT method for collecting spectra from dye mixtures (50 - 500 ng) extracted from small textile samples (2 mm yarn) is outlined. Results of experiments using library search routines for matching of IR spectra of simple (< 5 components) dye mixtures indicate that matches can be distinguished satisfactorily, however, with complex (8 - 14 components) dye mixture matching of duplicate spectra is less well defined. The application of principal component analysis for matching and discrimination of small dye extracts from a worn garment suggests that this is a useful approach and can add to the TLC information about the sample.
Enhancement of infrared absorption in silver-coated silicon oil films
Author(s):
V. N. Spiridonov;
V. A. Yakovlev;
Guerman N. Zhizhin;
Peter Grosse;
B. Heinz
Show Abstract
The infrared absorption of silicon oil with metal overlayers was studied using attenuated total reflection (ATR) technique. It is shown that the presence of thin (40...100 angstroms) Ag films leads to significant enhancement of absorption band intensities.
Near-infrared microscope technique for obtaining quantitative and qualitative aqueous surfactant phase-diagram information from a single sample preparation
Author(s):
Curtis A. Marcott;
Richard L. Munyon;
Robert G. Laughlin
Show Abstract
A technique for studying the phase behavior of aqueous surfactant systems using near-infrared (NIR) microspectroscopy has been developed. All the phases which exist along a particular isotherm are formed by creating an interface between water and surfactant within a long (55 mm) 25-micrometers pathlength fused silica cell, and allowing the components to diffuse together. The temperature of the cell is controlled to within 0.1 degree(s)C between 25 and 85 degree(s)C. Analysis of the entire composition range is achieved using a Fourier transform infrared (FT- IR) spectrometer equipped with a CaF2 beam splitter, a tungsten-halogen source, and an infrared microscope with a InSb detector. The intensity of the water bend-stretch combination band at 5175 cm-1 is shown to be useful for quantitation. A study of the octyldimethylphosphine oxide/water system illustrates the quantitative potential of this technique.
Application of Micro-RAS to surface analysis of magnetic disks and heads
Author(s):
Yoshiko Nakao;
Michio Nakajima;
Fujio Harako
Show Abstract
The Micro-RAS was applied to the in situ detection of microscopic and local contaminants on the magnetic disks and heads, which sometimes limited the progress of the new technology for the developing HDD. As a result, we succeeded in detecting and identifying the surface contaminants with the Micro-RAS, which had never been detected with the normal Micro-IR. The enhancement factor of the Micro-RAS to the Micro-IR was estimated to be about 20, especially for the detection of the adsorbed species whose vibrational mode was perpendicular to the surface.
Qualification of mechanically fabricated IR filters using FTIR spectroscopy
Author(s):
W. Bier;
Andreas E. Guber
Show Abstract
A new method for the mechanical manufacturing of microstructured bodies has been developed by the Karisruhe Nuclear Research Center in cooperation with the MesserschmittBôlkow-Blohm company, Munich-Ottobrunn. This technique is based on the surface structuring of foils by means of high-precision machining using, for example, rectangular profiled microdiamondsi. In Fig. 1, a scanning electron microscopy (SEM) of a 100 pm thick aluminum foil with a rectangular groove structure is shown. If copper foils, which have been microstructured in the same way, are stacked on top of each other and are subjected to diffusion welding, finely structured bodies are obtained which are covered by a multitude of microscopically small channels (Fig. 2). The copper body shown possesses approximately 8700 channels/cm2. The optical transparency is about 57 %. The length of the microstructure samples is freely optional within wide limits.
FTIR study of the poly(ethylene oxide)-resorcinol molecular complex
Author(s):
M. Dosiere
Show Abstract
The occurrence of a PEO-resorcinol molecular complex has been reported by Myasnikova et (1) and Cheng et j(2) The phase diagram shows that a bell-shaped region, centred about a 2:1 stoichiometry (i.e. two PEO monomer units for one resorcinol molecule) which separates two eutectic points°. From an X-ray investigation, Myasnikova et al. proposed a monoclinic unit cell: a=1.605 nm, b=1.425 nm, c=0.984 nm, = 1 12° and the space group, P2 1/a• This unit cell contains four chains, where four PEO monomer units are associated with two resorcinol molecu1es°. Recently, it has been shown by differential scanning calorimetry that the poly(ethylene oxide)-resorcinol molecular complex crystallizes into two allotropic forms, denoted as a and B forms, respectively(3). The cx form of the molecular complex crystallizes as unbanded spherulites. The reflections of the wide angle X-ray patterns from stretched film and spherulite of the a form are indexed on the basis of an orthorhombic unit cell, (a= 1.050 nm; b= 1.0132 nm; c= 0.9776 nm), with Pfl1 space group. This unit cell widely differs from the monoclinic unit cell previously reported by Myasnikova et This paper is devoted to the FTIR study of both allotropic forms of the PEO-resorcinol molecular complex.
Adsorption/desorption of substituted pyridines as probe molecules for surface acidities studied by Fourier transform infrared spectroscopy
Author(s):
X. Bouquet;
D. Lam;
Bruno Amram
Show Abstract
We determined what kind of original information (in comparison with the classical pyridine adsorption) could bring substituted pyridines (2,6-dimethyl pyridine called DMP, and 2,6-di- tert-butyl pyridine called DTBP) as probe molecules for surface acidities studied by Fourier- transform infrared spectroscopy in our industrial research laboratory. The three probe molecules were adsorbed on pure compound pellets and studied by transmission in a vacuum cell with variable temperature placed in the sample compartment of a NICOLET 7199 FTIR spectrometer. By performing single and competitive adsorptions, and desorptions at increasing temperatures for the three probe molecules on various compounds ((gamma) and flash alumina), we obtained a very useful tool. After an important work of spectral attribution, the main observations were: (1) Because of its stronger basicity, DMP detects Broensted (proton donor sites unseen by pyridine (phenomenon ruled by basicity). (2) DMP can also detect simultaneously Lewis (electron acceptor) sites on which it can be displaced by pyridine, which then recovers all its Lewis sites. This phenomenon has been interpreted as being ruled by steric effects. (3) DTBP allowed us to differentiate two types of Lewis sites on (gamma) and flash alumina: (a) a first type of acid sites due to electron-deficient oxygens on which DTBP molecules can be chemisorbed and can be displaced by pyridine (type I), and (b) a second type of acid sites only accessible to pyridine through the Al cation (type II). Pyridine, DMP, and DTBP adsorptions, with the help of variable temperature desorptions and also competitive adsorptions, studied by transmission Fourier-transform infrared spectroscopy were then shown to constitute a very informative tool for acid surface expertise in our industrial research laboratory because of chemisorption phenomena ruled by basicity and steric hindrance.
Layered semiconductor structures FTS diagnostics
Author(s):
K. Boltar;
Valeri A. Fedirko
Show Abstract
IR reflectance spectra of Si and GaAs/GaAlAs structures with as many as up to 5 surface layers have been measured. Model spectra have been constructed and compared with measured ones. The fitting procedure gives the layers thickness, the free charge carriers concentration and the mole fraction of AlAs in AlGaAs in each layer.
FTIR analysis of food poisons
Author(s):
Sritana C. Yasui
Show Abstract
Single and rapid analyses of chemical poisons or contaminants in different food matrices are explored. Various FT-IR accessories are utilized and compared for the detection sensitivity. Detection enhancements by combining with chromatographic techniques are investigated.
Adsorption of EDTA-type compounds on alumina surface
Author(s):
Janusz Ryczkowski;
Gabor Keresztury
Show Abstract
Highly dispersed nickel alumina supported catalysts have been prepared by the method of double impregnation. Application of an EDTA-type chelating agent in the first step of impregnation resulted in high metal dispersion in an active phase of the reduced catalysts. Results obtained from recorded spectras by Fourier transform infrared spectroscopy (FTIR) suggests chelating compound adsorption on alumina surface in the way of interaction between electron pairs on nitrogens and protonated surface hydroxyl groups.
Site structure in the electronic and IR spectra of porphyrin
Author(s):
J. G. Radziszewski;
Josef Michl;
Jacek Waluk
Show Abstract
The spectra of porphyrin isolated in low temperature noble gas and nitrogen matrices reveal a multiplet structure consisting of pairs of sites (A and B) which may be interconverted as a result of photo-induced double proton transfer. Single-site spectra are obtained for IR, electronic absorption, fluorescence and phosphorescence. Analysis of different magnitudes and signs of site-splittings in the IR spectra may be helpful for vibrational assignments.
Process control using fiber optics and Fourier transform infrared spectroscopy
Author(s):
E. K. Kemsley;
Reginald H. Wilson
Show Abstract
A process control system has been constructed using optical fibers interfaced to a Fourier transform infrared (FT-IR) spectrometer, to achieve remote spectroscopic analysis of food samples during processing. The multichannel interface accommodates six fibers, allowing the sequential observation of up to six samples. Novel fiber-optic sampling cells have been constructed, including transmission and attenuated total reflectance (ATR) designs. Different fiber types have been evaluated; in particular, plastic clad silica (PCS) and zirconium fluoride fibers. Processes investigated have included the dilution of fruit juice concentrate, and the addition of alcohol to fruit syrup. Suitable algorithms have been written which use the results of spectroscopic measurements to control and monitor the course of each process, by actuating devices such as valves and switches.
FTS study of magnetic transitions in cuprates R2Cu2O5 and R2BaCuO5
Author(s):
G. G. Chepurko;
I. V. Paukov;
Marina N. Popova
Show Abstract
A simple method was developed to obtain high resolution FTIR spectra of powder samples at low temperatures. The method was used to study magnetic ordering in the cuprates R2Cu2O5 and R2BaCuO5 (R -- rare earth or yttrium) related to high-Tc superconductors of the 123 type. Diffuse transmittance spectra due to f-f optical transitions in the intrinsic R3+ ion or Er3+ probe were measured at 2 - 120 K employing BOMEM DA3.002 FT spectrometer.
Time-resolved vibrational spectroscopy of liquid crystals and polymer films using step-scan 2-D FTIR
Author(s):
Vasilis G. Gregoriou;
James L. Chao;
Hirokazu Toriumi;
Curtis A. Marcott;
Isao Noda;
Richard Alan Palmer
Show Abstract
The application of step-scan interferometry to the determination of two-dimensional infrared (2-D FT-IR) spectra is reported here. Two experiments are discussed; the first monitors the dynamic changes in the IR transmission spectrum of a polymer film due to the application of a small amplitude oscillatory stress. The other experiment involves a study of the kinetics of reorientation of uniaxially aligned nematic liquid crystals under the influence of external ac electric fields. In both cases, the dynamic IR signals originate from the reorientation of the electric-dipole transition moments, and thus provide information at the molecular level about the macroscopic behavior of the systems under investigation.
Applications of step-scan FTIR photoacoustic depth profiling
Author(s):
Rebecca M. Dittmar;
Richard Alan Palmer;
James L. Chao
Show Abstract
The use of step-scan Fourier transform infrared (FT-IR) spectroscopy combined with photoacoustic (PA) detection is used to depth profile laminated polymeric materials. Depth profiling can be performed using a combination of the modulation frequency dependence and phase lag of the PA signal.
K300 Fourier transform spectrometer: environmental applications of the double-pendulum interferometer
Author(s):
Hermann Bittner;
Markus Erhard;
I. Neureither;
Herbert W. Mosebach;
Harald Rippel
Show Abstract
The described double pendulum interferometer is a newly designed FTIR spectrometer based on the Michelson interferometer type. The unique optical layout allows a compact design in spite of high resolution and offers a very high stability. The presented device K300 is constructed as a stable instrument for field measurements. Apart from absorption measurements of trace gases, an innovation in the field of environmental measurements is the monitoring of smoke stack pollution by remote sensing. First results of emission as well as absorption measurements are presented.
New compact Fourier transform spectrometer for the near-infrared and visible
Author(s):
Manfred Zeidler;
Peter Grosse
Show Abstract
In the near-infrared and visible (5000...25,000 cm-1) spectroscopy is often carried out by diffraction gratings. Fourier transform spectrometers need a high mechanical accuracy which could only be realized by a greater expense, corresponding to higher costs. But if we consider that for many applications a resolution of 50 cm-1 is sufficient, we could build an interferometer in a simple way. From the resolution it follows that a path difference of only 100 micrometers of the movable mirror is required, if a conventional Michelson interferometer is used. The idea is to make use of an ordinary piezoelectric translator doing this travel, which leads to a simple and low-cost construction. First measurements indicated that inaccuracies due to the mechanical design are below the tolerance limits (precision and reliability of the guide piece of the movable mirror). Furthermore, transmission spectra of different samples show good agreement to equivalent measurements done by a diffraction grating. So this apparatus could be an interesting alternative to some commercial instruments.
Thermal degradation studies in polyacrylonitrile in air using FTIR spectroscopy
Author(s):
Rita A. Raja;
T. S. Varadarajan
Show Abstract
Several workers have studied the thermal degradation of polyacrylonitrile using infrared spectra. The present study involves the spectral changes in the infrared spectra of PAN films degraded at temperatures of 150 - 245 degree(s)C and treatment times of 3 - 48 hours.
Infrared photoluminescence investigations on narrow-bandgap Hg1-xCdxTe
Author(s):
Frank Fuchs;
Peter Koidl;
K. Schwarz
Show Abstract
We report on Fourier transform photoluminescence studies, carried out on bulk crystals of Hg1-xCdxTe with narrow band-gap. Two different experimental techniques are discussed to detect weak luminescence signals in the presence of dominant thermal background radiation. Examples for luminescence measurements in the mid-infrared spectral range (8 - 12 micrometers ), as well as in the far infrared (70 micrometers ) are presented.
Calibration of a Fourier transform spectrometer using three black body sources
Author(s):
Volker Tank;
Erwin Lindermeir;
H. Dietl
Show Abstract
A procedure to calibrate a Fourier transform spectrometer is presented. Blackbody sources of three different temperatures are used to eliminate errors in the calibration arising from the limited accuracy of the temperature measurement of the calibration sources. With three spectra of blackbodies it is possible to assume that the temperatures are unknown variables, as are the parameters of the functions describing the spectrometer. Nonlinear Gaussian balancing calculation is applied to determine these unknown variables and to minimize the influence of noise. A comparison between results obtained with this method and a conventional calibration procedure is presented.
Basic measurements for the determination of concentrations of trace gases from emission spectra
Author(s):
Erwin Lindermeir
Show Abstract
With a Fourier-transform spectrometer, emission spectra of mixtures of gases are measured in the laboratory. These laboratory measurements are performed to simulate measurements of exhaust gases at smoke stacks. The aim of the work is the development of measurement methods and evaluation algorithms to determine the concentrations of the constituents of exhaust gases from remotely measured spectra of the infrared radiation of the plume.
Carbon dioxide line positions in the 780 to 940 wavenumber region
Author(s):
Mark P. Esplin;
Michael L. Hoke
Show Abstract
Spectra of a 40 torr CO2 sample heated to 800 K has been recorded at high resolution in the 780 to 940 cm-1 spectral region using the Air Force Geophysics Laboratory high-resolution interferometer. A total of 8 different rotation-vibration bands were identified. The measured line positions were used in a least-squares-fit to obtain updated rotational- vibrational constants.
Rot-step ATR spectroscopy
Author(s):
Kurt Palm;
Thomas Schwager
Show Abstract
Polarized infrared attenuated-total-reflection (ATR) techniques were tested on stretched polyvinylidendifluoride for molecular orientation.
Design and performance of a dynamically aligned step-scan interferometer
Author(s):
Richard A. Crocombe;
Raul Curbelo;
John C. Leonardi;
David J. Johnson
Show Abstract
In the past decade advances in microprocessors have been applied in FT-IR spectrometers to deliver higher data system performance at substantially reduced cost. Now, advances in microprocessors and signal processing technology are being applied to overcome current performance limits in the FT-IR optical bench, and considerably expand their functionality. This paper describes the design and performance of a new generation of research-grade interferometer, the 896, using state-of-the-art technology. The major enhancements are: rapid auto-align (allowing interchanging of beamsplitters); dynamic alignment (giving active stabilization and allowing high performance operation over a wide variety of scan conditions); enhanced stability rapid-scan mode with general purpose kinetic software; step-scan mode (0.004 Hz to 800 Hz) with variable phase modulation; and dynamic range extension.
TGA/FTIR and DSC/FTIR: combined approaches to solving problems
Author(s):
David A. C. Compton;
Jay R. Powell;
Richard A. Crocombe
Show Abstract
Thermal analysis of complex samples has been greatly assisted by the coupling of FT-IR analysis to the TA experiment, and evolved gas analysis by infrared spectroscopy has been very successful in combined TGA/FT-IR experiments. During a combined DSC/FT-IR experiment the FT-IR analysis is performed on the sample itself, by using an infrared transmitting microscope. A curing reaction and thermal changes in a polymer are used to demonstrate the use of a combined DSC/FT-IR system. By combining a simultaneous TGA/DSC instrument with FT-IR evolved gas analysis, we are now able to obtain three sets of complementary information, on the same sample, in one experiment. A study of the thermal behavior of zinc stearate is reported by using TGA/DSC/FT-IR.
Applications of a dynamically aligned, rapid- and step-scan interferometer
Author(s):
Richard A. Crocombe;
Senja V. Compton;
John C. Leonardi
Show Abstract
Step-scanning FT-IR has recently attracted increasing attention, and has novel applications in photoacoustic spectroscopy, time-resolved spectroscopy, and in multiple modulation experiments like vibrational dichroism (where clear separation of the frequencies is critical) and 2-D IR studies. The design and performance of a new dynamically-aligned interferometer which is capable of kinetic scan rates, conventional rapid-scanning, and also step-scan operation have been described. This paper discusses applications of this interferometer.
FTIR gas chromatographic analysis of perfumes
Author(s):
H. Diederich;
Phillip J. Stout;
Stephen L. Hill;
K. Krishnan
Show Abstract
Perfumes, natural or synthetic, are complex mixtures consisting of numerous components. Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) techniques have been extensively utilized for the analysis of perfumes and essential oils. A limited number of perfume samples have also been analyzed by FT-IR gas chromatographic (GC-FTIR) techniques. Most of the latter studies have been performed using the conventional light pipe (LP) based GC-FTIR systems. In recent years, cold-trapping (in a matrix or neat) GC-FTIR systems have become available. The cold-trapping systems are capable of sub-nanogram sensitivities. In this paper, comparison data between the LP and the neat cold-trapping GC- FTIR systems is presented. The neat cold-trapping interface is known as Tracer. The results of GC-FTIR analysis of some commercial perfumes is also presented. For comparison of LP and Tracer GC-FTIR systems, a reference (synthetic) mixture containing 16 major and numerous minor constituents was used. The components of the mixture are the compounds commonly encountered in commercial perfumes. The GC-FTIR spectra of the reference mixture was obtained under identical chromatographic conditions from an LP and a Tracer system. A comparison of the two sets of data thus generated do indeed show the enhanced sensitivity level of the Tracer system. The comparison also shows that some of the major components detected by the Tracer system were absent from the LP data. Closer examination reveals that these compounds undergo thermal decomposition on contact with the hot gold surface that is part of the LP system. GC-FTIR data were obtained for three commercial perfume samples. The major components of these samples could easily be identified by spectra search against a digitized spectral library created using the Tracer data from the reference mixture.
Commercial cryogenic Fourier transform spectrometer for emission measurements of materials
Author(s):
Jean Giroux;
Daniel Lamarre;
J. McKinnon;
Henry L. Buijs
Show Abstract
The cryogenic interferometer is an optimized sensor for low level infrared spectral measurements. An ideal application is emissivity measurements of low-temperature samples, since room temperature spectrometers become background limited by instrument self-emission in such cases. For a cryogenic instrument, operation near background limited performance for targets at 220 K with emissivity of 0.05 is possible by cooling the complete instrument to around 77 K. This instrument has been designed for operation in the laboratory, and most of the parameters are remote controlled by the data processing PC. Spectral resolution is variable from 4 cm-1 to 128 cm-1. The spectral range covered is from 600 cm-1 to 4000 cm-1. The system is built into an Infrared Lab Cryostat, providing a holding time of 48 hours. This instrument is the second cryogenic spectrometer built by Bomem, the first being the balloon-borne SIRIS, a high resolution system for atmospheric research.
Radiometric calibration and performance analysis of Fourier transform emission spectrometers
Author(s):
Daniel Lamarre;
Jean Giroux;
Henry L. Buijs
Show Abstract
FTIR instruments aimed at low temperature emission measurements require a two-point radiometric calibration because of significant emission from the instrument itself. Calibration measurements with two reference blackbodies are conducted for ground instruments. In space, the low temperature reference blackbody can be substituted with deep space observation. On the ground, pointing at a liquid nitrogen bath is used. Calibration operations involve complex arithmetics to obtain from reference and actual scene measurements a calibrated spectrum. Frequency and duration of calibration measurements are dependent upon instrument stability and noise budgets. When reference spectra are free of high resolution features, calibration measurements can be performed at a resolution lower than that of actual scene measurements. The Michelson interferometer for passive atmospheric sounding (MIPAS) will limb sound the atmosphere by measuring its mid-infrared emission with an apodized resolution of 0.05 cm-1. This instrument is used as an example to illustrate the trade-offs required in calibrating an emission FTIR. Given the current expected temperature variations of the instrument over the orbit, MIPAS will require a deep space reference measurement after every altitude scan, and a combined deep space and blackbody measurement at a lower frequency. For an adequate acquisition efficiency, low resolution calibration measurements are performed, at 0.2 cm-1 or 1 cm(superscript -1.
Spectroscopic requirements for optical characterization of semiconductor materials
Author(s):
Andre J. Villemaire;
Abel Zacharie;
Henry L. Buijs
Show Abstract
Semiconductor materials are used for the fabrication of devices for electronic and optical applications. Optical characterization techniques are among the most powerful methods to assess the general quality of semiconductor crystals. The optical methods can determine impurity content as well as assessing crystal morphology. They can also be used to study other properties of newly created materials. In practical terms they are non-destructive and simple to perform (no contacts required). Optical characterization methods monitor electronic transitions, local vibrational modes and other processes inside the material studied. The photons associated with these transitions carry very precise information about energy levels of the pure material and those induced by the presence of the impurities. These assaying methods can be classified under two general categories, according to the way the optical signature is supplied. Emission-type measurements include photoluminescence and Raman spectroscopy while absorption-type measurements include IR absorption, photocurrent and photothermal ionization spectroscopy (PTIS).
Selective detection of molecular ions and free radicals by FTS
Author(s):
Guy Guelachvili;
Pierre Martin;
A. Benidar
Show Abstract
Methods for the selective detection of molecular ions and free radicals in the gas phase by high resolution emission Fourier transform spectroscopy are described: velocity modulation and dual-beam optical subtraction for molecular ions and concentration, or population, modulation for radicals. Examples are given for ArH+ and OH radical.
FTIR studies of photochemical reactions of carbonyl sulfide with ozone
Author(s):
K. Jaeger;
R. Weller;
Otto Schrems
Show Abstract
Photo-oxidation reactions of carbonyl sulfide (SCO) in the presence of O3 have been studied in laboratory experiments in the gas phase and in solid argon matrices under stratospheric irradiation conditions. The photolysis experiments performed indicate that in matrices the reaction of O(1D) atoms with SCO providing CO2 + S as primary products is dominant, whereas in the gas phase the reaction O(3P) + SCO yields CO + SO becomes more important due to the rapid collisional quenching of O(1D). In matrices reaction products CO2, SO2, SO3, and SO4 could be identified.
Michelson interferometer with two rotating retroreflectors
Author(s):
Peter Haschberger
Show Abstract
A new device for FTS is introduced. Instead of a laterally moved plane mirror two rotating retroreflectors are used to generate the optical path difference. The new interferometer is especially suitable for mobile operation in the fields of environmental monitoring and remote sensing.
Design of grazing incidence and ATR objectives for FTIR microscopy
Author(s):
John A. Reffner;
Christopher Carl Alexay;
R. W. Hornlein
Show Abstract
The optical designs of the grazing incidence and the internal reflecting objective lenses for FT- IR microspectroscopy are described. Each of these lenses extends the FT-IR microscope's abilities for spectral analysis of microscopic samples. The function of both objectives is dependent upon the basic FT-IR microscope principals of remote aperture beam splitting and remote image plane masking. Dual remote confocal aperture masks are implicit for minimizing diffraction effects. These two objectives use Fourier plan masks to define the angular aperture of the incident radiation through the objective and onto the sample. These lenses are used for both imaging and spectral analysis
Molecular tissue mapping by FTIR microspectroscopy
Author(s):
John A. Reffner;
Frank M. Wasacz
Show Abstract
Determining the molecular chemical composition of human tissue is important to understanding its biochemistry. Variation in a tissue's biochemistry may result from normal changes in tissue type or from artifacts, which range from foreign materials trapped in tissue to the degeneration products associated with disease. While pathologists use light microscopy to identify abnormal areas of tissue, they can obtain only limited molecular information through staining or fluorescence methods. However, when microscopy and infrared spectroscopy are combined, they produce a powerful technique for probing the chemistry of different areas of tissue samples. In addition, the integration of FT-IR microanalysis with a scanning stage produces compositional maps that directly link molecular structure and morphology.
Characterization of the hydration state of pharmaceuticals by variable-temperature diffuse-reflectance infrared spectroscopy
Author(s):
Frank M. Wasacz;
Scott W. Strand;
David E. Bugay;
Kenneth R. Morris
Show Abstract
The characterization of hydrates is exceedingly important for pharmaceuticals since the state of hydration of a drug can effect its solubility, dissolution rate, bioavailability, chemical stability, and the physical stability of subsequent dosage forms. In addition, the United States Food and Drug Administration concerns about the above issue make complete characterization of hydrates a necessary part of investigative new drug filings. A Collector TM Diffuse Reflectance accessory fitted with a controlled Environmental Chamber was used to study drug formulations under varying temperature and humidity conditions.
Grazing angle microscopy: a new technique for surface analysis
Author(s):
John A. Reffner;
William T. Wihlborg;
M. C. Sweeney
Show Abstract
Grazing angle spectroscopy (GAS) has been extended to microscopic sampling areas by a special objective lens and an FT-IR research microscope. While the advantages of grazing incidence for the study of thin films on metals has been known and applied since the mid-1960s, GAS measurements have been limited to samples with large smooth flat surfaces. The grazing angle microscope objective reduces the scale of GAS samples from centimeters to micrometers. This reduction of the sampling area makes it possible to analyze samples with either small or irregular surfaces. In this work, specific examples are presented to illustrate that micro-GAS can yield useful data from samples too small or too irregularly shaped for conventional GAS. Specific examples of micro-GAS analyses are a lubricant film on a ball bearing, a surface film on an LDEF test panel, a boric acid solid lubricant on steel, and a polycarbonate-aluminum bonding surface.
FT-RAIRS study of alkyl radicals chemisorbed on single-crystal surfaces
Author(s):
Helmuth Hoffmann;
Francisco Zaera
Show Abstract
Alkyl radicals play a key role as reaction intermediates for many surface processes such as catalytic hydrocarbon synthesis or the degradation of coatings and lubricants. Their properties and reactivity on surfaces, however, are still poorly understood because simple synthetic routes to prepare them have not yet been developed and their identification among other hydrocarbon fragments requires highly specific and sensitive techniques. Using alkyl halides as precursors, we have prepared alkyl species on single crystal surfaces in an ultrahigh vacuum (UHV) environment and studied their surface chemistry by a combination of different surface science techniques. In this report we present an IR spectroscopic study on the formation of ethyl species from ethyl iodide and their decomposition on a Pt(111) surface.
FTIR studies of titanium tetrachloride and magnesium dichloride complexes with aromatic esters relevant to Ziegler-Natta catalysts
Author(s):
Kjell-Arne Solli;
Martin Ystenes;
Piotr Sobota
Show Abstract
Esters of aromatic carboxylic acids and dicarboxylic acids show different effects when used as electron donors in the synthesis of milled MgCl2-supported Ziegler-Natta catalysts. Such Ziegler-Natta catalysts are synthesized by cogrinding anhydrous MgCl2 with the ester, then reacting the resulting support with TiCl4 followed by washing and drying. Alternatively, the catalyst may be synthesized by cogrinding MgCl2 with a TiCl4- aromatic ester complex. The catalyst is activated by a trialkyl aluminum in order to polymerize propene or other (alpha) -alkenes. Esters of the monoacids generally enhance the activity of the catalyst (relative to no ester), and the produced polypropene is also more isotactic. Esters of the diacids also enhance the isotacticity of the polymer produced somewhat, but the activity of the catalyst is lower.
Quantitative determination of the fat, protein, lactose, and water content in cow milk using Fourier transform infrared spectrometry
Author(s):
Hendrik J. Luinge;
E. Hop;
E. T.G. Lutz;
John H. van der Maas;
A. Holstra;
H. A. van Hemert;
J. Koops;
H. Wooldrik;
E. A.M. de Jong;
G. Ellen
Show Abstract
In this paper the quantitative analysis of the four major components in cow milk using Fourier transform infrared spectrometry is described. Least squares regression using selected wavenumber regions is compared with full spectrum methods such as principal component regression (PCR) and partial least squares regression (PLS). Results are comparable with data obtained from infrared filter instruments with respect to precision and accuracy.
Application of a neural network to the identification of pesticides from their infrared spectra
Author(s):
Hendrik J. Luinge;
John H. van der Maas;
Tom Visser
Show Abstract
The results of preliminary investigations on the possible role of neural networks for the automated interpretation of infrared spectra are described. The performance of a three-layered neural net is compared to a library search system with respect to recognition of spectral patterns. Furthermore, the use of characteristic bandshapes is studied in order to improve the performance of automated interpretation systems.
Selective association of hydroxybenzenes with basket hosts: an FTIR study in dilute nonpolar solution
Author(s):
E. T.G. Lutz;
John H. van der Maas;
R. Sybesma;
R. J. M. Nolte
Show Abstract
Experimental evidence is found for different types of complexes that are formed when phenol and resorcinol associate with SmMe4 and Ph2RE basket type molecules. The symmetrical OH band of the complexes formed between resorcinol and SmMe4 is indicative for a bifurcated hydrogen bonded complex while the composed OH band in the other phenol, resorcinol complexes points to the presence of n and (pi) type OH(DOT)(DOT)(DOT)O equals C associates for SmMe4 and possibly additional OH(DOT)(DOT)(DOT)ether and OH(DOT)(DOT)(DOT)phenyl associates for Ph2RE.
Hydrogen bonding in crystalline beta-D-fructopyranose: a deuterium exchange and variable low-temperature FTIR study
Author(s):
E. T.G. Lutz;
J. S.J. Veldhuizen;
Hendrik J. Luinge;
John H. van der Maas;
J. Baran;
H. Ratajczak
Show Abstract
Variable temperature FT-IR spectra have been recorded of (beta) -D-fructopyranose in the range from 300 to 110 K. The drastic natural resolution enhancement showing up in the OH- stretching region upon cooling yields detailed information with respect to the H-bonded system in the crystalline phase. Based on deuterium exchange experiments we have shown experimentally the presence of vibrational coupling between some of the H-bonded OH groups. Using the spectral information of the noncoupled OH stretching vibrations we have made a tentative assignment in the OH-stretching region.
IR transmission cell for in-situ studies of reactions in solid and liquid phase in heterogeneous catalyst systems
Author(s):
Oystein Bache;
Martin Ystenes
Show Abstract
An in situ IR transmission cell for the study of different reactions in Ziegler-Natta catalyst systems is developed. The experimental setup makes it possible to: (1) simultaneously and separately study the reactions in the liquid and the solid phase of the heterogeneous system, (2) add controlled amounts of solute species and in situ follow the reaction, and (3) flush the solid phase with solvent to remove solute species. At present, reactions between AlEt3, ethyl benzoate (EB) and MgCl2 support are under study. The results show that free EB is present at an AlEt3/EB molar ratio of 3.3, indicating an unbalanced bridged adduct or an equilibrium situation. The results indicate (1) that no reduction of EB takes place at high AlEt3/EB molar ratio (max equals 14) at room temperature, and (2) that AlEt3 complexates with the support (internal donor (EB) and MgCl2) and forms a well defined compound. The results also indicate that the cell and experimental setup are well suited for these type of studies.
Fourier transform far-infrared studies on copper ion-exchanged zeolites Y
Author(s):
Rolf Piffer;
Horst Foerster
Show Abstract
Transition metal ion-exchanged zeolites offer outstanding catalytic properties due to their cations, representing one type of active center. Detection of their sites and accessibility to adsorbates are important goals of fundamental research. As extra-framework cations are indicated by translatory absorptions in the FIR, in-situ observation of their alterations upon admission of reactants should shed light on their role in catalysis. Copper-exchanged zeolite Y has proved to be highly active in butadiene cyclodimerization. This induced us to investigate this system in more detail.
Infrared photoacoustic spectra of adsorbed species on fine particles of metal and metal oxide
Author(s):
Yoshiko Nakao;
Haruka Yamada;
Mari Yamada
Show Abstract
By using the homemade PAS apparatus, PA spectra of dyes and surface active agents monomolecularly adsorbed on fine particles of Ag, NiO and ZnO could be clarified, and detailed information on the chemical bondings of adsorbed species was obtained. Stronger PA signal of the adsorbed species was observed on the metal oxides with smaller thermal conductivity than on the metal with larger one.
Measurements of biomass-burning emissions by FTIR spectroscopy
Author(s):
Dale F. Hurst;
David A. Twyford;
David W.T. Griffith
Show Abstract
The gaseous emissions of biomass fires are identified and quantified using two analytical techniques; gas-phase and matrix-isolation Fourier-transform infrared (FTIR) spectroscopy. The predominant carbon-based gas emissions of fires, CO2, CO and CH4, are assayed by gas-phase FTIR spectroscopy. Matrix-isolation FTIR spectroscopy is used to measure nitrogen-containing, sulphur-containing and the lesser carbonaceous gas emissions of fires. Through these measurements, we hope to estimate the impact of biomass burning on the global budgets of many important atmospheric trace gases.
FTIR studies of water-ozone complex in solid argon
Author(s):
K. Jaeger;
M. Wierzejewska-Hnat;
Otto Schrems
Show Abstract
Fourier Transform Infrared (FTIR) Spectroscopy combined with the matrix isolation technique was used to study 1:1 complexes formed between water and ozone in solid argon. The reactions of water-ozone complexes have been induced by narrow band photolysis at 250 nm and products could be identified in the spectra. Several isotopes of water (H2O, D2O, HDO and H218O) and ozone (16O3, 16,18O3 and 18O3) have been examined which allowed us to identify different isotropic modifications of the water-ozone complex and its photoproducts.
Diffuse-reflectance infrared Fourier transform spectra of crystalline and amorphous solids
Author(s):
Ch. Peuker;
E. Loeffler;
W. Pilz;
K.-H. Schnabel;
U. Zscherpel
Show Abstract
By using an IR diffuse reflectance technique it is possible to simplify various kinds of powder measurements, thus eliminating traditional sample preparation steps of grinding and pellet pressing. In addition, various experimental in situ arrangements can be realized more easily than in the corresponding transmission arrangement. The DRIFT technique has a great advantage for detecting weak absorption bands compared with common IR transmission. This work aims to demonstrate the advantage of DRIFT measurements to solve various chemical problems.
Modeling of smoke stack emissions for FTIR remote sensing
Author(s):
Rainer Haus;
Klaus Schaefer
Show Abstract
The K300 stack exhaust gas radiance measurements are simulated numerically by radiative transfer calculations. Atmospheric background and foreground influences are discussed, including aerosol scattering. A multicomponent analysis of measured spectra is performed.
Photometric accuracy of FTIR spectrometers
Author(s):
Markus I. Flik;
Z. M. Zhang
Show Abstract
High photometric accuracy is essential for precise measurements of optical properties. The effect of source radiation power on the photometric accuracy is a mechanism of growing importance, since modern FTIR spectrometers possess strong sources for high signal-to-noise ratio. A related problem is radiation incident on the detector from a high-temperature sample. This paper presents an analysis of the photometric error in the reflectance measurements for samples at high temperatures. The maximum temperature that can be investigated as a function of the required photometric accuracy is determined for several dielectric crystals and film- substrate composites.
Analysis of trace concentrations of contaminants in water by sparging-FTIR
Author(s):
Walter Mike Doyle
Show Abstract
This paper describes a new approach to monitoring organic contaminants in water in which a fixed fraction of each contaminant is transferred to a continuously flowing gas stream for analysis by an FTIR spectrometer. This approach provides near real time operation with measurement sensitivity in the low ppb range for many aromatics and chlorinated hydrocarbons.
Characterization of biotechnologically and medically relevant yeasts (fungi) by Fourier transform infrared spectroscopy
Author(s):
Ottmar Serfas;
Dieter Naumann;
Gabriele Standfuss;
Lutz Brueggemann;
Ingeborg Flemming
Show Abstract
The Fourier-transform infrared spectra of intact procaryotic cells (bacteria) have already been used in the past to characterize (differentiate, classify and identify) a variety of bacterial strains and taxa. In this paper the essential features of a methodology are described which extend the FT-IR pattern recognition approach to intact eucaryotic cells (yeasts/fungi). Basically, the characteristic information pertaining to microbial FT-IR patterns is explored by applying multivariate statistics and cluster analysis to both the time and frequency domain of the mid-ir spectral data.
In-situ characterization by FT-Raman spectroscopy of compounds separated on a thin layer chromatography plate
Author(s):
Peter Fredericks;
Christopher de Bakker;
Eric Martinez
Show Abstract
FT-Raman spectroscopy has been shown to be useful as a method of identifying compounds separated on a tlc plate. Commercial tlc plates, with or without UV fluorescent indicators, were found to be suitable for the technique provided that they had a metallic backing. Plates with polymer backing were unsuitable, as polymer bands could be seen in the spectrum. The method was demonstrated using a range of aromatic and aliphatic organic compounds.
Comparison of methods for determining linear birefringence
Author(s):
Peter Lampen;
Ernst Heiner Korte;
A. Blumenberg
Show Abstract
For the determination of the ordinary and extraordinary refractive indices of nematic liquid crystals in the infrared spectral region, a refractometer was developed. It is a critical angle refractometer of the Abbe type, basically usable in the range from n equals 1.3 to 1.8 and from 4000 cm-1 to 700 cm-1. The reliability of the measurements is 1 X 10-3 and the spectral resolution is 1.5%. The values of the refractive index derived from the critical angle are used as anchor points for Kramers-Kronig transformation (KKT) of a transmittance spectrum of the compound.
Optical properties of superthin niobium films deposited on crystalline quartz
Author(s):
L. A. Kuzik;
V. N. Spiridonov;
V. A. Yakovlev;
Guerman N. Zhizhin;
Fedor A. Pudonin;
Peter Grosse;
B. Heinz
Show Abstract
Optical properties of ultrathin metal (Nb) films (1.5 angstroms - 20 angstroms) on (alpha) - quartz have been studied. On quartz the metal films were prepared by radio frequency sputtering. Such films shows metallic behavior even for the thickness of a few angstroms. Then the samples were covered by a 50 angstroms Si protective film. As was found earlier, the imaginary part of dielectric function (Im(Epsilon) ) of Nb depends on the thickness nonmonotonically and has maximum at 6 angstroms. To study this effect in more detail we have used two sets of samples with thickness increasing from sample to sample on 2 angstroms and on 1.5 angstroms. All spectra were recorded using Fourier-transform spectrometer Michelson-110 (BOMEM).
Infrared emission of radio-frequency-excited (N2 + SiH4) discharge by high-resolution Fourier transform spectroscopy
Author(s):
Mohammed Elhanine;
Robert Farrenq;
Guy Guelachvili
Show Abstract
Infrared emission of a gas mixture of N2 and SiH4 activated by radio frequency discharge has been analyzed using high resolution Fourier transform information. In addition to the several electronic bands of N2, signatures of three transient species--namely, NH, SiN and SiNH--have already been identified. For iminosilicon SiNH this is the first gas phase spectroscopic observation. Molecular parameters have been derived with a high accuracy. For nitride silicon, radical new A2$PI - X2(Sigma) bands have been observed. These data have been combined with other available information in order to improve molecular structure.
Real-time infrared spectroscopy of moving solids for on-line analyses
Author(s):
Roger W. Jones;
Siquan Luo;
John F. McClelland
Show Abstract
Two related methods, transient infrared emission spectroscopy and transient infrared transmission spectroscopy, can obtain good spectra from opaque, moving solids by using a transient thermal gradient to isolate spectroscopically a thin layer of material. The basic elements of the methods, the ability to depth profile, and an application involving monitoring coating cure are described.
Application of factor analysis to FTIR microscopy
Author(s):
Steven M. Donahue;
John A. Reffner;
William T. Wihlborg;
A. W. Strawn
Show Abstract
Applying chemometrics methods to the analysis of FT-IR microscopy data extends and improves compositional mapping. With an FT-IR microscope, it is possible to record mid-IR spectra from areas as small as 5 X 5 micrometers 2 and to step-scan over large areas in a regular sequence, thereby recording an array of spectra for compositional mapping. Initially, compositional maps were produced by inspecting individual spectra to identify an absorption that changed intensity with its coordinates in the data array. This band intensity would then be plotted against its spatial coordinates to produce a three-dimensional composition map. This form of mapping was generally called 'functional group mapping.' However, these data sets can be analyzed more effectively by using chemometrics principals to derive detailed quantitative maps and 'pure' principal-component spectra. The factor analysis also reduces the data set and improves the signal-to-noise ratio of compositional maps. Factor mapping has been applied to identify and plot the distribution of polymer film contaminates, foreign bodies in tissues, and adhesive bonding layers in polymer laminates. In addition, this combination of FT-IR microscopy and chemometrics has been used to test the uniformity of polymer blends and alloys. These examples are presented to illustrate the general applicability of these technologies and the strength of their union.
Diagnostic of noise at an interferometer by Fourier transformation of disturbances
Author(s):
H. O. Tittel;
D. Wissmann
Show Abstract
Mechanical and electromagnetic disturbances, source noise included, introduce noise and 'satellite-lines' into the spectrum. Usually these effects are reduced by computing an average interferogram from individual measurements. We describe a method to identify such noise sources by their own frequency spectrum and thus offer a possibility to eliminate them at their origin. Some examples are presented.
FT spectrometer with fixed mirrors using Fizeau fringes
Author(s):
J. Linkemann;
Fernando Romero-Borja;
H. O. Tittel
Show Abstract
We present a Fourier Transform spectrometer where as an interferogram, fringes of equal thickness (Fizeau fringes) are recorded instead of the usual fringes of equal inclination (Haidinger rings). An image of the Fizeau fringes being formed on the diode array of a CCD camera allows us to scan the interferogram without moving a mirror or any other element. As the entire interferogram is registered at the same time, AC and even pulsed light sources can be analyzed. The disadvantage is low spectral resolution because the maximum path difference is limited by the size of the diode array.
Optical characterization of superconductive thin films by dispersive FT spectroscopy
Author(s):
Fernando Romero-Borja;
J. Linkemann;
H. O. Tittel;
R. Stenzel
Show Abstract
Some preliminary room-temperature measurements on thin-films superconductors using Dispersive Fourier Transform Spectroscopy (DFTS) in reflection are presented. Directly measured phase and amplitude reflectivity spectra in visible light are used to illustrate experimental difficulties when trying to determine optical properties of these materials. Some observations about the surface quality of the samples are discussed in connection with the obtained results.
UV-VIS Fourier transform spectrometer with automatic adjustment
Author(s):
R. Stenzel;
W. F. Bluhm;
H. O. Tittel;
Fernando Romero-Borja
Show Abstract
We present an UV-VIS Fourier Transform spectrometer with dynamic alignment and, in addition, automatic adjustment of the moving mirror before start and at each change of translation direction. In dynamic alignment the phase difference of laser interferograms from three points of the field of view is used to activate transducers holding the moving mirror. Whenever a run of the mirror is finished there is no interferogram for a few moments till the next run starts. The direction of translation is now opposite and due to the discontinuity of frictional forces in the drive there can be a misalignment of the moving mirror. If the misalignment leads to a phase difference greater than (pi) between the laser interferograms, correct alignment cannot be refound. To overcome this difficulty one can generate many laser interferograms instead of only three. Unless the interferograms from neighbor spots are out of phase by more than (pi) , the mirror can be realigned. Another solution of the problem which we present here is to modify the tilt of the moving mirror by means of piezo translators until the visibility of the interferogram of an expanded laser beam is at maximum.
Fourier spectroscopy with a transputer-based standard image processing system
Author(s):
W. Weihs;
M. Rost;
A. Noll
Show Abstract
A CCD camera setup is introduced which can be used to digitize the interferogram data of the Fizeau fringes of a Fourier spectrometer. To decrease costs we use a standard CCD chip (frame type) for digitization. It is cooled by a Peltier element which allows it to work even with relatively faint light sources. The frame grabber as well as the final analysis processor are Inmos T800 transputer based modules. Using these electronics the instrument is even capable of measuring spectra of slightly pulsed light sources.
T800-based transputer data acquisition and analyzing system for a Fourier spectrometer
Author(s):
W. Weihs;
M. Rost;
B. Nteife
Show Abstract
Hardware and software of a processor system based on INMOS T800 transputers are introduced. They allow data acquisition, correction and a fast final analysis for a high resolution Fourier spectrometer as well as the real-time generation of the appropriate control and steering signals of the apparatus, thus allowing a direct automatic adjustment.
Using FTIR spectroscopy and FTIR microscopy for the examination of wood and wood tissue
Author(s):
Oskar Faix;
James H. Boettcher;
E. Bertelt
Show Abstract
FTIR spectroscopy and FTIR microscopy are powerful tools not only for the analysis of lignins or celluloses but also for research on whole wood. Spectra of four lignocelluloses are presented and an application of FTIR microscopy for the analysis of an unknown inclusion in wood is shown.
Novel fiber optic cell for infrared analysis
Author(s):
Michael P. Fuller;
Timothy E. May;
Steven R. Lowry;
Becky Green
Show Abstract
Over the last few years a number of uses of chalcogenide fibers for analyses in the mid infrared have been described. This paper will describe a new approach using a tapered mid infrared fiber as part of a commercial accessory.
Advances in infrared microspectroscopic imaging
Author(s):
Forrest J. Weesner;
Richard T. Carl;
Ross M. Boyle
Show Abstract
This paper reports on the application of an interferogram-based data reduction routine to infrared microspectroscopic imaging. The Gram-Schmidt (GS) orthogonalization procedure, popularized in application to GC-IR data, was used to measure the infrared response across the surface of the samples. A set of interferogram segments is selected to form an orthonormalized basis set describing background conditions. Basis information is subtracted from the interferograms collected at each sampling location resulting in a vector containing information distinct from the basis. The magnitude of the sample vector is the GS response, a measure of difference from the basis.
Surface infrared spectroscopy using a dual-channel polarization-modulation spectrometer
Author(s):
Matthew J. Smith;
Robert Dueval;
Robert M. Corn
Show Abstract
The sensitivity of an FT-IR spectrometer for measuring monolayers and other thin films can be enhanced if one takes advantage of the surface selection rule to reduce the dynamic range of the experiment. This is accomplished in polarization modulation infrared reflection-absorption (PM-IRRAS) by rapid modulation (74 KHz) of the linear polarization of the incident light , and subsequent demodulation of the detector signal. PM-IRRAS yields a differential signal which contains only the surface information. This differential signal is usually ratioed against the total reflectance signal to yield the spectrum of interest. Normally, two sequential measurements are required. First, the differential signal is acquired, then the total reflectance measurement is made. However, a better method is to use the dual channel approach first described by Buffeteau, et. al.1 The principal advantage of this method is that all isotropic (i.e. atmospheric and nonsurface) absorptions are perfectly ratioed.
Intrazeolite carbonyl metal chemistry: in-situ diffuse-reflectance infrared Fourier transform investigation
Author(s):
H. Boulet-Desgrousilliers;
C. P. Bremard;
Christophe Depecker;
P. Legrand
Show Abstract
Diffuse Reflectance Infrared Fourier Transform Spectroscopic (DRIFTS) investigations indicate that under thermal activation, the coadsorption, by vapor-phase loading of benzene in the Na85%/X faujasite-type zeolite leads to the grafted Mo(CO3 moiety, whereas (n6-C6H6) Mo(CO)3 is obtained in Na55Y; no reaction is observed in the dealuminated Y* zeolite before the desorption on both benzene and Mo(CO)6.
Reproducibility in mid-IR diffuse-reflectance spectroscopy for quantitative analysis
Author(s):
F. De Lene Mirouze;
Jean Pierre Huvenne;
P. Legrand;
J. C. Boulou
Show Abstract
Three devices for quantitative analysis have been compared. They significantly improve the reproducibility compared to manual packing methods. Their performances for quantitative analysis are similar. However the press filling method can be more easily automated.
FT-Raman investigations of highly colored compounds
Author(s):
Christophe Depecker;
P. Legrand;
J. C. Merlin;
B. Sombret
Show Abstract
A preliminary investigation of the vibrational properties of anthocyanidins, the most important group of plant pigments, is presented. The results indicate that the visible chromophore is mainly located on the benzopyrylium moiety and emphasize the complementarity of FT-Raman analysis in regard to resonance Raman (RR) and infrared spectroscopies for highly colored compounds.
Direct structural characterization of agar on red algae by FTIR microspectrometry
Author(s):
C. Declerck;
M. Sekkal;
B. Sombret;
Jean Pierre Huvenne;
P. Legrand;
J. C. Mollet;
M. C. Verdus
Show Abstract
FTIR microspectrometry is used to control the quality of agar directly in algae microtom cuts. The gelling ability which defines the quality of this polysaccharide depends on the degree of the galactose unit. FTIR microspectrometry is a powerful tool which responds to our needs because we must analyze small samples (diameter of about 10 micrometers ) coming directly from algae or little quantities of extracted agar. However, the presence of components other than agar in the algae forces us to include other chemical and theoretical methods to achieve our purpose.
Control of separation and quantitative analysis by GC-FTIR
Author(s):
A. Semmoud;
Jean Pierre Huvenne;
P. Legrand
Show Abstract
Software for 3-D representations of the 'Absorbance-Wavenumber-Retention time' is used to control the quality of the GC separation. Spectral information given by the FTIR detection allows the user to be sure that a chromatographic peak is 'pure.' The analysis of peppermint essential oil is presented as an example. This assurance is absolutely required for quantitative applications. In these conditions, we have worked out a quantitative analysis of caffeine. Correlation coefficients between integrated absorbance measurements and concentration of caffeine are discussed at two steps of the data treatment.
Quantitative analysis of aqueous solutions by FTIR spectroscopy of dry extract
Author(s):
N. Dupuy;
M. Meurens;
B. Sombret;
P. Legrand
Show Abstract
Continuing the approach adopted by Meurens et al. in dispersive NIR spectroscopy, the principle of using dry extracts is taken up in FTIR spectroscopy, yielding three advantages: the rapidity of Fourier transform spectroscopy, the solvent elimination, and a better peak resolution in the mid-IR. However, sampling appears more difficult in mid-IR than in NIR spectroscopy. In mid-IR spectroscopy, particular dry extract problems are: (1) the nature and the choice of the support, (2) the reproducibility of the signal, and (3) the feasibility of quantitative analysis. The performances of our dry-extract method are required here in terms of spectroscopy as well as of a multicomponent quantitative analysis of mixed sugars in aqueous solutions.
Far-infrared spectra, conformational stability, and barriers to internal rotation of some substituted 3-chloropropenes
Author(s):
T. G. Costner;
T. S. Little;
Douglas T. Durig;
James R. Durig
Show Abstract
The far-infrared spectrum (375 to 30 cm-1) of gaseous 2,3-dichloropropene has been recorded at a resolution of 0.06 cm-1. The fundamental asymmetric torsional mode is observed at 91.9 cm-1 with eight excited states falling to low frequency for the s-cis (chlorine atom eclipsing the double bond) conformer. Utilizing the s-cis torsional frequency, the gauche dihedral angle and the enthalpy difference between conformers, the potential function governing the interconversion of the rotamers has been calculated. The determined potential function coefficients are (in cm-1): V1 equals 1047 +/- 96, V2 equals -619 +/- 68, V3 equals 1216 +/- 50, and V4 equals 26 +/- 22, with an enthalpy difference between the more stable s-cis and gauche conformers of 245 +/- 30 cm-1 (0.70 +/- 0.09 kcal/mol). Similarly, the fundamental asymmetric torsion for the more stable gauche conformer of trans- 1,3-dichloropropene has been observed in the far infrared spectrum of the gas at 84.0 cm-1. The corresponding mode for the s-cis conformer gives rise to a series of well defined C-type Q branches beginning at 129.8 cm-1. From these data the potential function governing internal rotation of the asymmetric top has been determined and the potential coefficients are: V1 equals -558 +/- 7, V2 equals -38 +/- 10, V3 equals 637 +/- 9, V4 equals 174 +/- 7, V6 equals -16 +/- 4 cm-1. From studies of the Raman and infrared spectra of the gas at variable temperatures, the conformational enthalpy difference has been determined to be 342 +/- 36 cm-1 (978 +/- 103 cal/mol). All of these data are compared to the corresponding quantities obtained from ab initio Hartree-Fock gradient calculations employing either the 3-21G* or 6-31G* basis sets.
Pyrolysis GC/FID/FTIR, pyrolysis GC/MS, and FTIR studies of dried peat water samples differing in botanical composition and geographical location
Author(s):
Wayne M. Zunic;
Suyan Ding;
James R. Durig
Show Abstract
Six peat water samples differing in botanical composition and geographical location, along with a humic acid standard, were characterized using pyrolysis GC/FID/FTIR, pyrolysis GC/MS, and FTIR spectroscopy. Pyrolysis GC/FID/FTIR analysis revealed many by-products resulting from the thermal degradation of the major constituents of plant material: cellulose and lignin. Comparison of the pyrolysis chromatograms showed large variations in the chemical compositions of the pyrolysis products from sample to sample. Results of the FTIR analysis revealed major differences around 1000 cm-1 (C - O stretch region) and between 1500 and 1800 cm-1 (C equals C and C equals O stretch region). These two regions have previously been identified as representing cellulose and lignin, respectively. The six different peat water samples are compared based on their resulting FTIR spectra and pyrolysis chromatograms along with a comparison to the humic acid standard. Similarities and differences are emphasized along with any conclusions drawn based on these studies.
Far-infrared spectrum and barriers to internal rotation of propanal
Author(s):
Gamil A. Guirgis;
W. E. Brewer;
Jian Liu;
Stephen Bell;
James R. Durig
Show Abstract
The far-infrared spectrum has been recorded from 50 to 360 cm-1 at a resolution of 0.10 cm-1 for propanol, CH3CH2CHO, as well as for three additional isotopic species, CH3CH2CDO, CH3CD2CHO, and CD3CD2CHO. The fundamental methyl torsional transitions have been observed for both the s-cis and gauche conformers for all four isotopic species from which the threefold barriers to internal rotation have been calculated. For the gauche conformer V3 equals 1040 +/- 50 cm-1 and V6 equals 23 +/- 11 cm-1, and for the s-cis conformer V3 equals 850 +/- 50 cm-1. The asymmetric torsional transitions for each isotopic species have also been assigned, and the potential function governing the internal rotation of the CHO rotor has been determined. The data include significant coupling between the symmetric and asymmetric rotors.
FTIR study of carbon fibers used in medical applications
Author(s):
Marta Blazewicz;
Czeslawa Paluszkiewicz
Show Abstract
The Fourier Transform Infrared (FTIR) spectroscopy method was used to investigate the structural changes to which active carbon fibers are subjected in a biological environment. Infrared spectra for the fibers retrieved from animal tissue indicate that active carbon fibers lose the carbon structure properties and transform into an organic phase with physicochemical properties close to that of biological tissues.
Basic experiments in TLC/FT-Raman spectrometry
Author(s):
Axel Rau
Show Abstract
In some basic experiments, the feasibility is demonstrated of getting artifact and fluorescence free spectra by in-situ FT-Raman spectrometry of TLC spots. In addition, the high sensitivity enhancement by using TLC/FT-SERS of silver colloid activated chromatographic spots is shown.
Sampling problems in Fourier transform photoluminescence and their consequences on the computed spectra
Author(s):
Carlo Lamberti;
Almerino Antolini
Show Abstract
We have performed photoluminescence (PL) measurements on III - V semiconductor materials. InP and related compounds, used in fiber-optic communication. The PL radiation is excited with an argon laser ((lambda) equals 488 nm) and collected by a liquid nitrogen cooled Ge detector (spectral range 5800 - 15000 cm-1). The sampling of the PL signal, using a He-Ne reference laser, occurs every (Delta) d equals (lambda) REF/2 equals 316.4 nm of the optical path difference (OPD) due to the displacement of the movable mirror; the maximum wavenumber detectable, without aliasing problems, is (sigma) M equals 1/2 (Delta) d 15803 (cm-1). In a real instrument, considering the possibility of small errors in the position of the movable mirror, the value of the OPD dj in the sampled points is given by dj equals -L + j(Delta) d + (epsilon) (d), j equals 0,1,2,...N - 1, where L is the maximum displacement of the movable mirror, N is the number of sampled points and (epsilon) (d) is the error in the value of the OPD caused by an erroneous position of the movable mirror.
FTIR spectra of Keggin-type heteropolyanions inserted into conjugated polymer matrices
Author(s):
Miroslaw Handke;
M. Hasik;
Czeslawa Paluszkiewicz;
A. Pron;
I. Kulszewicz-Bajer
Show Abstract
12-heteropolyacids (HPA) constitute a large group of compounds with a characteristic anion structure and general formula H8-nX+nM12O40, where X equals P, As, Ge, Si and M equals W, Mo, V. These compounds are widely applied as catalysts, behave as strong acids, and some of them exhibit significant redox properties as well. Recently it has been discovered that HPA can act as a dopant, i.e., convert conjugated polymer chains from their neutral state to the oxidized (polyacetylene, polypyrrole) or protonated (polyaniline) state. Such doping reaction involves simultaneous insertion of heteropolyanions between the chains of polymers possessing an extended (pi) bonding system. The resulting compounds exhibit very interesting catalytic properties. In this paper, FT-IR spectroscopy has been applied to characterize heteropolyanions inserted into conjugated polymer matrices.
Temperature- and atmosphere-controlled drift spectra of H3+nPMo12-nVnO40-type heteropolyacids with Keggin structure
Author(s):
Miroslaw Handke;
K. Bruckman;
Czeslawa Paluszkiewicz;
W. Paw
Show Abstract
Heteropolyacids (HPAs) are compounds widely applied in different catalytic processes. They have been used as acid catalysts and also as oxidation catalysts at elevated temperatures. Therefore, from the catalytic point of view it is important to know the thermal behavior of these compounds under reduction and oxidation conditions as well. Although several studies on the thermal properties have been reported, also by means of in situ IR spectroscopy, little is known about decomposition of HPAs, in controlled atmosphere. In this study we examined in situ by DRIFT spectroscopy the solid state heteropolyacids at temperature range 295 K - 723 K in both dry nitrogen and oxygen atmospheres.
Fourier deconvolution of the amide I FTIR band of insulin-polyamino acid complexes as related to conformation
Author(s):
K. Herzog;
K. Braun;
G. Losse
Show Abstract
Fourier deconvolution has been employed to enhance the resolution of the amide I FTIR band of different insulin polyamino acid complexes and mixtures. The broad band was resolved into several components. The overall shape of the amide I band of complexes and mixtures was found to be nearly Lorentzian. Therefore a Lorentzian function was used for the deconvolution. The resolved band components were assigned to specific protein conformations.
Application of FT-Raman spectroscopy to the study of polymer materials
Author(s):
Hideyuki Ishida;
Akira Ishitani;
K. Krishnan
Show Abstract
FT Raman spectroscopy has been applied to the characterization of polymer alloy and polyethylene terephthalate (PET) films treated under various conditions. Near-infrared YAG laser excitation has enabled the measurement of the Raman spectra of highly fluorescent colored polymer alloys. Molecular interaction between two blended components has been examined by the subtraction method. It has also been demonstrated that the curve-resolving technique of carbonyl Raman band can be very useful for the study of microstructures of PET.
Fourier transform spectroscopy semiconductor photodetectors peculiarity
Author(s):
Vitaly I. Stafeev;
K. O. Boltar;
L. D. Saginov
Show Abstract
Using Fourier Transform Spectroscopy (FTS), we have measured HgCdTe diodes and resistors photoresponse at wavelengths below the fundamental absorption edge in this semiconductor. This study is inherent to FTS photoresponse and is performed by the long wavelength radiation modulation of the short wavelength photocurrent. Possible physical mechanisms of such modulation are discussed.
Infrared spectroscopic investigations on the chemical modification of the wool fiber surface
Author(s):
J. Delhey;
Ursula Schumacher-Hamedat;
Hartwig Hoecker
Show Abstract
In industry, textiles usually are dry cleaned with perchloroethylene (C2Cl4), which has the reputation of being toxic. Therefore investigations to substitute this solvent by alternative and environmentally unobjectionable solvents are of great importance. The fiber surface after solvent treatment and the distribution of residual grease are examined by FTIR spectroscopy.
Infrared spectroscopic investigations (grazing angle reflection, polarized ATR) on the conformation of thin poly(aminoacid) films
Author(s):
Chr. Hoenings;
Ursula Schumacher-Hamedat;
Hartwig Hoecker
Show Abstract
Oxidative pretreatment for printing of wool fabrics is necessary to degenerate the fiber surface in order to improve dyestuff absorption. Industrially applied chlorination causes environmental problems. A new method based on catalyzed hydrogen peroxide was developed. FT-IR- investigations in different techniques (KBr-pellet, ATR, diamond optical anvil cell) gave information about the degree of oxidation of the wool fibers, in particular the fiber surface, and the dyestuff absorption.
Infrared spectroscopic investigations on the distribution of residual grease on textiles
Author(s):
J. Siedler;
Ursula Schumacher-Hamedat;
Hartwig Hoecker
Show Abstract
Surface modification of textile materials is of major importance in the modern textile industry. Several methods are commonly applied to produce a broad range of coated materials. The adhesion between the coating polymers and the textile fibers often determines the quality. Improved adhesion of the coating is achieved by a chemical bonding (covalent or ionic) between the coating materials and the textile. The efficiency,however, is dependent on the orientation of the functional groups of the outmost molecular layers of the fibers. Therefore, we have used surface sensitive methods to analyze the surface structure of proteinaceous fibers. Homopoly(aminoacid) films like poly(-(gamma) -benzyl-L-glutamate) and poly(- (Beta) -benzyl-L-aspartate) have been chosen as models for natural fibers like wool.
Variable low-temperature FTIR study of crystalline sugars
Author(s):
E. T.G. Lutz;
John H. van der Maas;
F. B. van Duijneveldt;
J. A. Kanters;
J. Baran;
H. Ratajczak
Show Abstract
The complex chains of hydrogen bonds of (Beta) -L-arabinose (I), methyl (alpha) -D- glucopyranoside (II) and di-(Beta) -D-fructopyranose 1,2':2,1'-dianhydride (III) in the crystalline state have been studied at variable low temperature. In addition to the increase of information showing up in the overall region upon cooling, the effect on intensity, bandshape and bandmaximum has also been studied. Most surprising is the contradictive behavior of the shift of the band maxima of methyl (alpha) -D-glucopyranoside, for which an increase is observed for the 'free' OH group, while H-bonds absorbing at lower wave-numbers are red shifted. Deuterium exchange experiments show the presence of vibrational coupling in the crystal of II whereas this phenomenon is absent in III.
Applications of new spectroscopic data transfer standards
Author(s):
A. N. Davies;
H. Hillig;
Peter Lampen;
I. Tuerpe;
M. Linscheid
Show Abstract
The implementation of spectroscopic data transfer standards is becoming increasingly important for academic and industrial data processing. With the development and implementation of new spectroscopic data transfer standards the possibilities for the flow of information between scientists has been greatly increased. Recent developments that will affect the work of the spectroscopist are outlined. The benefits and some of the possible pitfalls are highlighted.
IR-ATR spectroscopic determination of the diffusion coefficients of carbohydrates in polymer matrices
Author(s):
E. Rosenberg;
Robert A. Kellner
Show Abstract
During the past few years, the importance of membranes in chemical and biotechnological applications, such as separation processes and biosensor construction, has dramatically increased. As a consequence, membrane properties have to be characterized very thoroughly with special respect to diffusivity and selectivity. Whereas most techniques for the determination of diffusion coefficients require sophisticated and often indirect methods for the detection of the analyte diffusing through the membrane, which generally do not allow monitoring of the diffusion process continuously, we present in this work an experimentally simple and straightforward method employing FTIR-ATR spectroscopy. The diffusion of glucose into a PVA membrane is chosen as a model example for the determination of carbohydrates in polymer matrices due to its special relevance in biosensor construction. The method is based on monitoring the time-dependent change in absorption due to the diffusion of the glucose into the polymer membrane. After reaching a steady-state, the normalized absorbance plot (A/A(infinity) ) versus time can be used for numerical evaluation. The diffusion coefficient is determined by comparing the experimental with simulated data using the membrane thickness (iota) and the diffusion coefficient D as simulation parameters. For this reason, the performance of a recursive and two non-recursive models for the description of the diffusion process is examined. Modifications in the second non-recursive algorithm finally resulted in very good agreement with the experimental data. This work marks the first application of IR-ATR spectroscopy for the determination of diffusion coefficients even as large as of the order of 10-6 cm2/sec.
FEFA sensor based on a chalcogenide MIR fiber coupled to an FTIR spectrometer
Author(s):
Karim Taga;
Robert A. Kellner
Show Abstract
The surface modification of a chalgogenide glass fiber by chemically bound enzymes is used for the construction of a fiber optic chemical IR sensor. The quality of the surface modification is recognized to be of significant importance for the sensor performance. IR-ATR spectroscopy and IR microscopy are used as in situ and ex situ techniques to control the quality of the fiber optic IR sensor.
Multivariate determination of blood substrates in human plasma by FT-NIR spectroscopy
Author(s):
Herbert Michael Heise;
Ralf Marbach;
Th. Koschinsky;
F. A. Gries
Show Abstract
A spectral analysis of human EDTA plasma from 124 different patients was undertaken using an FT-NIR spectrometer. Optimized intervals of the absorbance spectra were considered for the PLS-calibrations with reference concentrations from standard clinical methods determined in triplicate. The following relative prediction errors were achieved: total protein 1.4%, cholesterol 3.8%, triglycerides 8.6%, glucose 9.1%, and urea 18.6%.
Novel design of an ellipsoidal diffuse-reflectance accessory with improved throughput
Author(s):
Ralf Marbach;
Herbert Michael Heise
Show Abstract
The value of diffuse reflectance spectroscopy for infrared analytical methods has some limitations caused by the low throughput efficiency of commercial accessories. We have redesigned a home-built diffuse reflectance accessory with an on-axis ellipsoidal collecting mirror which can also have benefits for the analysis of bulky samples. For illumination, use is made of the Circle cell optics which fits by adaption into the cone with a half angle of 30 degree(s) not considered for detection. Special features of the accessory are discussed, especially in view of our applications to the study of human tissue.
Surface carbonyl species on highly dealuminated NaY zeolite: an FTIR investigation
Author(s):
H. Landmesser;
I. Burkhardt;
H. Miessner
Show Abstract
FT-IR spectroscopy has been used to study the rather rich surface chemistry of Rh, Ir and Ru supported on zeolites. Highly dealuminated zeolite Y (US-Ex) has proved to be an ideal matrix for the formation of well defined surface carbonyls with unusually sharp carbonyl stretching bands. As the result, dicarbonyls of Rh and Ir and a tricarbonyl of Ru could be clearly identified on the surface.
In-situ external reflection FTIR studies on the electrochemically polymerized polyphenylene
Author(s):
Carita Kvarnstrom;
A. Ivaska
Show Abstract
In situ external FTIR measurements were made on electrochemically polymerized polyphenylene film, made from biphenyl using acetonitrile as solvent and TBABF4, (tetrabutylammonium-tetrafluoroborate), as electrolyte salt. Effects of current density on the formation of oligomers and the ratio of ortho and para substituted polymer chains during film growth and the resulting chain length were studied. Polymer films, made from different dimer concentrations, where step-wise potential cycled in the electrolyte solution. Changes in the IR- spectrum of the film were studied when going from the neural to the oxidized and to the overoxidized states of the polymer. The amount of solvent, counterion and residual water still in the film or adsorbed on it were found to depend on the potential applied to the film. The ion content and transport in the films depended on the thickness of the film.
Far-infrared absorption in fractal structures
Author(s):
N. N. Ovsyuk;
V. N. Novikov
Show Abstract
Low-energy fractal vibrational excitations in polymers are investigated using Fourier transform spectroscopy. The superlocalization exponent d(phi ) equals 1.8 is determined.
Vibrational-circular-dichroism spectra of five methyl-substituted 6,8-dioxabicyclo[3.2.1]octanes
Author(s):
Thomas Eggimann;
Hal Wieser
Show Abstract
The vibrational circular dichroism (VCD) spectra of the title compounds were recorded in the range of 800 - 1500 cm-1 using a Nicolet 8000 FT-IR interferometer. They were assigned based on observed absorption spectra, calculated frequencies using scaled ab initio 3 - 21 G force fields, and 3 - 21 G atomic polar tensor (APT) intensities. To interpret the observed VCD features fixed partial charge (FPC), charge flow (CF) and APT intensities were used. APT reproduces the VCD intensities reasonably well. Complete matrices of STO-3G Mulliken charge flow parameters (CFPs) augmenting FPC-VCD intensities revealed charge flow governed modes and certain inadequacies of the CF model.
Vibrational-circular-dichroism spectra of alpha-pinene, beta-pinene, and nopinone
Author(s):
Felix Maurer;
Hal Wieser
Show Abstract
FT recorded vibrational circular dichroism (VCD) spectra of the title compounds (I to III) are reported for the region 800 - 1500 cm-1. They are interpreted based on observed absorption and Raman spectra, and ab initio force fields and intensities calculated at the 3 - 21 G level of theory. The VCD spectra are simulated with the semi-empirical models of atomic polar tensors (APT), fixed partial charges (FPC), and charge flow (CF) using one transferred charge flow parameter (CFP). The APT method satisfactorily reproduces the VCD band signs and relative intensities. The CF model is equally successful for most parts of the spectrum and considerably improves the FPC intensities for modes that involve C - O stretching.
Clustering from infrared spectral data of petroleum products
Author(s):
C. Anne Gilchrist;
John M. Tolchard
Show Abstract
The infrared spectrum of either a pure material or a complex mixture is unique to that substance. However, the IR spectra of complex mixtures containing components of a similar nature, such as crude oils and gasolines, exhibit only small differences. It is often difficult to distinguish between these spectra, because of their similarities, when examining large sets of data in conventional ways. Principal component analysis (pca) has been applied to IR data obtained from a range of petroleum-related products.
In-vivo near-infrared FT-Raman spectra of photosynthetic bacteria
Author(s):
K. Okada;
Y. Fujimoto;
S. Muraishi;
Y. Koyama;
Yukihiro Ozaki
Show Abstract
Near-infrared (NIR) excited FT-Raman spectra have been measured in vivo for whole living photosynthetic bacteria, Rb. sphaeroides G1C and R26. The obtained spectra have provided new insight into molecular interactions and environments of the 9-keto and 2-acetyl groups of bacteriochlorophyll-a (BChl-a) in the light-harvesting (LH) complexes.
Determination of polymer end and functional groups by NIR spectrometry
Author(s):
Sabine Haagen;
Detlef Drosdziok;
Gerd Reimann;
Klaus Wueller;
Joachim Oelichmann
Show Abstract
The knowledge of accurate hydroxyl and acid numbers as well as water content is of great value for process control and quality assurance in the polymer industry. Standard methods are lengthy procedures and require large quantities of chemicals. Therefore rapid and simple spectrometric determinations are preferable. Especially near-infrared spectrometry in combination with chemometric methods offers some distinct advantages for such applications. The properties of polyesters derived by principal components regression (PCR) are compared to results obtained from well-accepted standard methods. Good correlations are achieved for OH and COOH numbers and weaker, but still useful, correlations are also achieved for water content. Thus PCR of near-infrared spectra offers the potential to replace other methods of investigation that are time-consuming and expensive.
PLS quantitative infrared analysis of cocaine with diffuse-reflectance sampling
Author(s):
Edward G. Bartick;
Rena A. Merrill
Show Abstract
A procedure has been developed to determine the concentration of cocaine HCl in sugar matrices. Partial least squares (PLS) quantitative software was used to calibrate 100 - 0% cocaine in inositol, dextrose, lactose, and mannitol. Calibration correlation coefficients ranged from 0.999 to 0.977 depending on the frequency range and the standards used.
On-line detection for capillary and packed-column supercritical fluid chromatography by direct-deposition SFC-FTIR
Author(s):
Anthony S. Bonanno;
Kelly L. Norton;
Jyisy Yang;
Peter R. Griffiths
Show Abstract
Compounds separated by supercritical fluid chromatography (SFC) can be identified by Fourier transform infrared spectrometry (FT-IR) after direct deposition (DD) onto an infrared transparent substrate. This methodology has been demonstrated as an off-line technique by several groups'3. A logical extension to this technique is to collect the spectra of the eluting species on-line. This is demonstrated using a commercial DD GC/FT-IR interface4 with minor modifications. The transfer line is replaced with an integral restrictor which acts as both pressure restrictor and transfer line. The tip of the restrictor is held about 75 mfrom a cooled zinc selenide window. Since carbon dioxide expands to a gaseous state upon decompression, it can be pulled away by a moderate vacuum, and the eluting species are trapped as small spots (about 100 jm diameter) on the cooled window. During a chromatographic run the window is translated such that shortly after deposition the spots pass through the focused beam of an infrared spectrometer. The radiation is collected by a Schwartzchild microscope objective and focused at an adjustable aperture by a field lens. The size of this aperture determines the effective size of the beam at the zinc selenide window. The fraction of the beam transmitted by the aperture is refocused onto the element of an MCT detector by a second Schwartzchild objective. Since the two objectives are identical, maximum sensitivity is achieved with a detector element the size of the trapped siots (100 j.m).
Rapid characterization of GC-FTIR spectra by a PCA-based expert system
Author(s):
Erik J. Hasenoehrl;
Jonathan H. Perkins;
Peter R. Griffiths
Show Abstract
A capillary gas chromatographic separation with Fourier transform infrared identification (GC/FT-IR) can yield structural information about volatile and semivolatile components of a complex mixture to a minimum identifiable quantity of about 5 ng for polar compounds using a lightpipe detector. Three procedures for analyzing GC/FT-IR data are currently in common use. In order of increasing selectivity they are Gram-Schmidt (GS) reconstructions, wavelength-selective chromatograms, and spectral library searching. This paper describes an approach by which functional and structural information can be extracted rapidly and on-line in a GC analysis with a specificity that is intermediate between that of selective wavelength chromatograms and library searching. In this approach principal components analysis (PCA) is used to build expert system rules to characterize molecular structures in a similar manner to those which we have recently described.
Optical and thermal evaluation of transparent materials and surfaces by FTIR and integrating spheres
Author(s):
Ulrich Frei;
Michael Koehl
Show Abstract
Integrating sphere measurements are presented in the wavelength range from 0.35 micrometers to 18 micrometers . The spheres are used with a rapid scan FTIR Bruker IFS66. The design of the sphere allows the spectral reflectance and transmittance to be determined, both as normal hemispherical and as normal diffuse values. The excellent resolution and reproducibility is demonstrated by noise spectra and some measurements. The easy sample handling makes this instrument a versatile tool for the development of new materials as well as for aging investigations.
IR transparent hemispheres as internal reflection elements in polarization IR-ATR spectroscopy
Author(s):
Bojidar Jordanov;
Bernhard D. Schrader
Show Abstract
A gallium arsenide hemisphere mounted in a rotatable holder is used as an internal reflection element with a conventional ATR attachment for single reflection. Its main advantage consists in recording pure polarization spectra of both sample directions lying in the interfaces hemisphere/sample at any angle of incidence.
CD study of concentrated induced-cholesteric solutions
Author(s):
Bojidar Jordanov;
D. Tsankov;
D. Kolev;
Ernst Heiner Korte
Show Abstract
CD spectra of induced cholesteric solutions (solutions of optically active substances in nematic liquid crystals) exhibit two effects: CD band of selective reflection and CD absorption, the latter being manifested at each solvent band. Due to the low concentration of the optically active guest substance the solute bands usually remain hidden. This paper is an attempt to detect solute bands in the CD spectra of induced cholesteric solutions.
Improved FTIR measurement of optical rotatory dispersion
Author(s):
D. Tsankov;
Bojidar Jordanov
Show Abstract
An improved method for measuring IR-ORD by means of FT-IR spectroscopy is suggested. Its advantage consists in doubling the angle of rotation of the polarization plane and in its technical convenience. Examples with induced cholesteric solutions are presented.
Applications of vibrational spectroscopy: microscopy in materials science and characterization
Author(s):
John M. Chalmers;
Jeffrey G. Eaves;
Neil J. Everall;
Wendy F. Gaskin;
Janet Lumsdon;
Norman Moore
Show Abstract
Infrared and Raman spectrometers coupled to optical microscopes provide the spectroscopist with powerful tools for the identification, characterization and mapping of materials using high spatial resolution. Each combination has its own attributes and many applications; the emphasis here is placed on the determination of the molecular structure and physical properties in polymers and composites.
Rotational analysis of nitrogen trifluoride
Author(s):
Joseph K. McDonald;
Wayne M. Zunic;
James R. Durig
Show Abstract
High resolution spectra (0.004 cm-1) of all of the fundamental bands of nitrogen trifluoride have been obtained. Rotational analysis of these bands has produced better band constants than had previously been reported.
Analysis of photochemical reaction kinetics by FTIR spectra intermolecular photocycloaddition of o-chloranil
Author(s):
H. Betterman;
H.-J. Schroers
Show Abstract
The photochemical reaction of o—chloranil (3 ,4,5,6 —tetrachioro— 1 ,2 —benzoquinone) was initiated by the excitation of the lowest energetic l(fl_fl*) state using emission lines of an argon ion laser1 . The data of liquid chromatography establish that only one final compound is generated. The photoproduct has dimeric structure identified by mass spectroscopy. The isotopic distribution of the molecular peaks closely corresponds to the isotopic pattern of octachloro—substituted molecules. Moreover, the mass spectrum exhibits the stepwise loss of two carbon monoxide groups. This feature is characteristic for quinones. The dimeric photoproduct reveals that the reaction can be described by an intermolecular [4+21 photocycloaddltion. In contrast to the reaction of 3,5—di--tert.-butyl—1,2—benzoquinone (investigated under same conditions) in which an absorption band (at 2134 cm') of CO dissolved in the reaction mixture was visible, a parallel CO abstraction can be excluded.
FTIR and 1H MAS NMR investigations on the correlation between the frequency of stretching vibration and the chemical shift of surface OH groups of solids
Author(s):
Eike Brunner;
H. G. Karge;
H. Pfeifer
Show Abstract
The study of surface hydroxyl groups of solids, especially of zeolites, belongs to the 'classical' topics of IR spectroscopy since physico-chemical information may be derived from the wavenumber (nu) OH of the stretching vibration of the different hydroxyls. On the other hand, the last decade has seen the development of high resolution solid-state NMR spectroscopy and through the use of the so-called magic-angle-spinning technique (MAS) the signals of different hydroxyl species can be resolved in the 1H NMR spectra of solids. The chemical shift (delta) H describing the position of these lines may be used as well as (nu) OH to characterize quantitatively the strength of acidity of surface OH groups of solids. In a first comparison of (nu) OH with (delta) H for several types of surface OH groups, a linear correlation between them could be found. The aim of this paper was to prove the validity of this correlation for a wide variety of hydroxyls. The IR measurements were carried out on a Perkin-Elmer FTIR spectrometer 1800 at the Fritz Haber Institute of the Max Planck Society, Berlin, and the 1H MAS NMR spectra were recorded on a Bruker MSL- 300 at the University of Leipzig.
Influence of adsorbed molecules on the positions of the combination and overtone vibrations of surface OH groups
Author(s):
Uwe Zscherpel;
B. Staudte;
K. Beck
Show Abstract
The goal of this study was to determine the influence of adsorbed molecules on the OH bending vibration, which cannot be directly measured in the fundamental region (750 - 1050 cm-1) because of the strong lattice vibrations of the substrate. The only way is to measure the combination vibrations in the near infrared. The Diffuse Reflectance Infrared Fourier Transform (DRIFT) technique was used to study the whole spectral range from the fundamental vibrations of OH groups to the overtones in the near infrared (3000 - 7500 cm-1) on the same sample. Several OH groups with different acidity on silica and crystalline alumosilica (zeolites) have been investigated.
Measured performance of a Hadamard-coded photodiode-array spectrometer
Author(s):
Joseph L. Robichaud;
Wallace K. Wong;
Roger A. Van Tassel
Show Abstract
We report performance measurements of a photodiode array Hadamard transform spectrometer (HTS) with a stationary entrance mask. The high throughput of the multi-slit, no- moving parts instrument is shown to yield a significantly higher S/N ratio than a single-slit array spectrometer. In addition, we examine sources of instrument noise and propose techniques to further enhance system performance.
Application of Fourier transform infrared spectroscopy to examination of documents
Author(s):
Janina Zieba-Palus;
Beata Trzcinska
Show Abstract
Some 30 samples of writing and wrapping paper were examined using two techniques: transmission (as a KBr disc) and diffuse reflectance. About 15 blue ball pen ink samples were extracted directly from the document by means of a C2H5OH - CHCl3 mixture using an extraction apparatus which enables the separation of impurities (coming from a paper) from the extracted ball pen inks. Infrared spectra were measured on a Digilab Fourier transform spectrometer FTS-15 within the range 400 - 3800 cm-1. Statistical inference based on T2 Hotelling's test to assess the significance of differences observed in IR spectra of samples without examining the origin and essence of those differences was applied. The analysis of the spectral data was performed on a IBM-AT computer.
Near-infrared Fourier transform spectroscopy of gases
Author(s):
C. D. Dyer;
P. J. Hendra;
C. J. Petty
Show Abstract
Raman spectra of several glass gases have been recorded using near-infrared (NIR) excitation and a Fourier transform (FT) spectrometer. This has been accomplished by designing a multiple reflection cell suitable for use in the 180-degree backscattering geometry used on the spectrometer. Initial studies have concerned N2, Cl2, CH4, CH3Br, and CS2. Further developments are discussed.
In-situ FTIR investigation on lead electrodes in 5-M sulfuric acid: formation and consumption of lead sulphate
Author(s):
G. L.J. Trettenhahn;
G. E. Nauer;
A. Neckel
Show Abstract
By external reflection-absorption in situ FTIR spectroscopy, the generation of PbSO4 on Pb-electrodes in 5 M sulfuric acid was investigated. It was possible to monitor the process of lead sulphate formation (oxidation) during anodic polarization and of lead sulphate consumption (reduction) during cathodic polarization. A correlation exists between the electric charge passed through the lead electrode and the intensity of absorption bands of lead sulphate.
FTIR-ATR evaluation of topical skin protectants useful for sulfur mustard and related compounds
Author(s):
Ernest H. Braue Jr.;
Marty R. Litchfield;
Catherine R. Bangledorf;
Robert G. Rieder
Show Abstract
The US Army has a need to develop topical protectants that can decrease the effects of cutaneous exposure to chemical warfare (CW) agents. Such materials would enhance a soldier's ability to carry out the mission in a chemically hostile environment, would lessen the burden on medical personnel, and may allow the casualties to return to duty in a shorter period of time than might otherwise be possible. In a preliminary report (E. H. Braue, Jr. and M. G. Pannella, Applied Spectrosc., 44, 1061 (1990)), we described a unique analytical method using FT-IR spectroscopy and the horizontal attenuated total reflectance (ATR) accessory for evaluating the effectiveness of topical skin protectants (TSPs) against penetration by chemical agents. We now describe the application of this method to the chemical warfare agent sulfur mustard (HD).
Polyurethane monitoring by mid-infrared fiber Fourier transform spectrometry
Author(s):
James A. de Haseth;
Jennifer E. Andrews
Show Abstract
Chalcogenide fibers that transmit radiation in the mid-infrared region have been coupled to a Fourier transform infrared spectrometer. The fibers are used to measure attenuated total reflectance spectra of samples that are remote, or do not lend themselves to conventional sampling methods. The samples used in this study are polyurethane foams and spectra are collected while the foams are forming. The reaction intermediates can be monitored, as well as the reaction kinetics. Spectra can be collected rapidly; faster than one spectrum per second, however, the reaction rates in this study do not require temporal resolutions of faster than 10 seconds. The collected spectra are subjected to factor analysis to identify the reactants, intermediates and products.
Infrared absorption-reflection spectroscopy of long chain alcohols at the air-water interface
Author(s):
Arne Gericke;
Heinrich Huehnerfuss;
Alexander V. Michailov
Show Abstract
Infrared Reflection-Absorption Spectroscopy (IRAS) is a very useful tool to investigate the conformation of amphiphiles at the air/water interface. Herein, monomolecular films consisting of 1-hexadecanol were studied using different incident angles and states of polarization. It is shown that for s-polarization the bands are negative, and the intensities decrease with increasing angles of incidence. For p-polarization, negative bands are only encountered at small incidence angles, while at large incidence angles the bands become positive.
ATR investigations of BaF2 and PbF2 films
Author(s):
Wolfgang Heerdegen
Show Abstract
Reflection spectroscopy in the infrared is used for studying small selective energy losses in optical coatings. New environmental effects at BaF2 and PbF2 films are detected.
Laser-induced infrared fluorescence of ytterbium atoms
Author(s):
K. Bollweg;
G. H. Guthoehrlein;
Laurentius Windholz
Show Abstract
In carrying out laser-induced fluorescence experiments within a low pressure discharge containing ytterbium atoms we observed a remarkable behavior of the fluorescence phases relative to the laser modulation of a three level subsystem in the ytterbium atomic spectrum. (The detected fluorescence radiation lies in the near infrared region, accessible both to a standard fourier spectrometer and a grating spectrometer). The effect will be discussed and modelled.
FTIR spectra of the solid solutions (Na0.88K0.12)VO3, (Na0.5K0.5)VO3, and Na(V0.66P0.34)O3
Author(s):
D. de Waal;
A. M. Heyns
Show Abstract
It is known that three different solid solutions, (Na0.88K0.12)VO3, (Na0.5K0.5)VO3 and Na(V0.66P0.34)O3, form in the (Na,K)(V,P)O3 system. These compounds all have monoclinic crystal structures similar to the pure alkali metal metavanadates containing small cations, e.g. Li+ and Na+ (Space group C2/c). Metavanadates with large cations like K+, Rb+, C+s and NH+4 form orthorhombic crystals, space group Pbcm. All those are structurally related to the silicate pyroxenes. Na(V0.66P0.34)O3 and (Na0.88K0.12)VO3 have the same modified diopside structure as (alpha) - NaVO3 while (Na0.5K0.5)VO3 adopts the true diopside structure. The infrared spectra of the three solid solutions are reported here in comparison with those of (alpha) -NaVO3 and KVO3. The results are also correlated with those obtained in two independent high pressure Raman studies of NH4VO3 and RbVO3 as the introduction of a larger cation like K+ should increase the pressure in the structure.
Structural analysis of DNA oligomers in single crystals and in aqueous solutions by micro-FTIR and Raman spectroscopy
Author(s):
Heinz Fabian;
W. Hoelzer;
Dieter Naumann;
H. Welfle;
U. Heinemann
Show Abstract
Being interested in the effects of base sequence and environmental conditions on the DNA structure, we have analyzed the solution and crystal structures of some G/C-rich DNA oligomers by vibrational spectroscopy. Here, we report on the analysis of the octamer d(GGGATCCC) and the decamer d(CCAGGCCTGG). Raman spectra were recorded on a Raman spectrometer as in, infrared spectra were measured with a Fourier transform infrared spectrophotometer Bruker IFS-66, for infrared measurements on crystals, the IFS-66 was coupled to an IR-microscope.
FTIR linear study of transition from a lamellar to an inverted micellar phase
Author(s):
Anders Nilsson;
Allan Holmgren
Show Abstract
The lamellar (L(alpha )) and inverted micellar (L2) phases of the system monooleoylglycerol/water (MO/water), have been studied by FTIR-spectroscopy, using the linear dichroism (LD) technique. The order parameter of functional groups in MO are calculated. These order parameters were examined during the thermotropic phase transition from the oriented lamellar phase to the isotropic inverted micellar phase. When the temperature is increased the order parameter of the MO molecules decreases faster in the polar head region as compared with the acyl chain region. At the phase transition temperature (43 degree(s)C) the order parameter (S) approaches zero. The half-width of the carbonyl band increases 2 cm-1 when the temperature is increased from 30 degree(s)C to 45 degree(s)C. This increase may be due to an increased hydration of the carbonyl group.
FTIR spectroscopy studies on epoxy networks
Author(s):
T. Scherzer;
Veronika Strehmel;
W. Taenzer;
S. Wartewig
Show Abstract
FTIR spectroscopy was used to study epoxy resins cured with amine or modified with diols. The influence of an accelerator on the epoxy/amine system was investigated. The structure of the epoxy/diol networks is dependent on diol chain length and concentration.
Surfactant monolayers at the air-water interface
Author(s):
Yei-Shin Tung;
Leslie J. Fina
Show Abstract
Surfactant monolayers are formed by the adsorption of dodecane sulfonate sodium salt from bulk aqueous solutions to the air-water interface. The reflection-absorption of polarized infrared radiation from the surface is probed with respect to the bulk concentration of the water soluble surfactant and the concentration of sodium chloride in the subphase. The anisotropic orientation of the amphiphiles is calculated by using optical modeling equations. Inferences about the conformation of the alkyl chain are made from frequency information.
Similarity analysis of infrared spectra
Author(s):
Hartmut Hobert;
Kathrin Meyer;
Michael Meyer
Show Abstract
A set of infrared spectra is transformed into a set of scores vectors by a principal component analysis. Cluster or display procedures show the similarity relations in these vectors. The usefulness of this approach is demonstrated by the classification of urinary stones.
Upgrading the database by Fourier transform spectrometry
Author(s):
R. C. Learner;
G. Nave;
J. E. Murray;
Juliet Pickering;
Anne P. Thorne;
James W. Brault
Show Abstract
Current work with the visible-UV FT spectrometer at Imperial College is directed at improving the data base for the astrophysically and analytically important transition elements, using complementary data from the IR obtained at the National Solar Observatory, starting with iron, chromium and cobalt. This paper highlights the gains and problems of FTS for this type of work.
Use of principal components analysis for detailed observation of the effects of deformation and relaxation on the C=O stretching band of a block polyurethane
Author(s):
Charles E. Miller;
Nicholas M. Reynolds
Show Abstract
A thin film of a block polyurethane copolymer (with a poly(tetramethylene oxide) soft segment, and a hard segment derived from butanediol and piperizine), was used for this study. FTIR spectra (in the C equals O region, 1650 to 1750 cm-1, 2 cm-1 nominal resolution) were collected during deformation and relaxation by a Nicolet 60SX FTIR spectrometer that was adapted to a stretching apparatus. Spectra at 20% extension intervals were collected as the sample was stretched to 200% extension, relaxed to 60% extension, and re-stretched to 300% extension. Principal components analysis of the spectra (after baseline correction, normalization, and subtraction of the average spectrum from all of the spectra) was performed with the UNSCRAMBLER software package (CAMO A/S, Trondheim, Norway).
Transmission, emission, and specular-reflection FTIR spectra of the thin forsterite (MG2SiO4) film
Author(s):
Miroslaw Handke;
Anna Stoch;
Witold Jastrzebski
Show Abstract
The forsterite ceramics is a promising material for electric and engineering applications because of its low dielectric loss and low thermal expansion coefficient. The aim of this work is to characterize the thin films of forsterite deposited on steel sheet and silicon wafer by means of FT-IR spectroscopy. In the case of thin films on a flat solid surface the most useful IR measurement technique is specular reflection. However, as it was reported in many papers, these spectra may differ drastically from the transmission spectra. Therefore, the second aim of this work is the comparison between forsterite films's spectra recorded with different sampling techniques including specular reflection, transmission and emission.
Seeing more, looking at less: applications of IR microscopy
Author(s):
Peter Grosse;
Lukas Kuepper;
Wolfgang Theiss
Show Abstract
Applications of IR microscopy in solid state physics are shown, namely, the investigations of layer thickness variations in semiconductor systems and of the scattering characteristics of small particles, both making use of the ability to take spectra from small sample spots.
Brain mapping by FTIR microspectroscopy
Author(s):
David L. Wetzel;
Steven M. Le Vine
Show Abstract
Spatial resolution achieved with a state-of-the-art scanning molecular FT-IR microspectrometer allows excellent spectra to be obtained from relatively small areas of 8 micrometers thick section of brain tissue. Concentration mapping is achieved by picking absorbances or baseline-corrected absorbances of select peaks for each scan obtained at a particular x,y coordinate of the tissue section. Scanning was done in the transmission mode and a programmable microscope stage was used to position the specimen in the beam between scans. The chemical selectivity of the microspectroscopic technique allowed us to superimpose chemical data onto the spatially-defined structures, particularly myelin, in the brain. Since the chemical information is both qualitative and semiquantitative the heterogeneous distribution is revealed. Previously spectroscopic analysis was performed on myelin fractions obtained from brain homogenates. This did not allows observation of localized concentration differences, as is now the case. In addition to spectra, maps of selected key wavelength responses presented from frozen sections of normal brains, result in chemically selective distribution profiles in the gray matter, white matter and basal ganglia.
FTIR characterization of heparinizable polymer-coated materials for application in biomedicine
Author(s):
Rolando Barbucci;
Agnese Magnani
Show Abstract
Fourier Transform Attenuated Total Reflection Infrared Spectroscopy (ATR/FTIR) was used for surface characterization of some commercial materials used in the biomedical field [polyurethane (PU), plasticized polyvinylchloride (PVC), glass, polytetrafluoroethylene (Goretex) and polyethyleneterephthalate (Dacron)] coated with a well-characterized heparin-complexing biomaterial (PUPA) based on polyurethane and poly(amido-amine) components. In particular, difference spectroscopy was used to analyze the coating-substrate interaction to which the material stability is related, and the heparin-material surface binding.
Quantitative FT-NIR of thermochemical properties of industrial organic fluids
Author(s):
David L. Wetzel;
Arnold J. Eilert
Show Abstract
Near-IR quantitative analysis is now well-established using multivariate statistical expressions. This has been particularly useful for routine industrial applications. Mainly filter instruments have been used industrially. However grating monochromators, and more recently acousto- optic tunable filter and FT-NIR instruments are available for use. The practicality of FT-NIR for industrial quantitative monitoring has been subject to question. In this work, quantitation was performed on all three types of scanning instruments. Unlike mid-IR, in near-IR it is necessary to quantitate relatively weak absorption differences measured in a few milliabsorbance units. In the past, most FT-NIR was done with modified FT-IR instruments. Dedicated FT-NIR instruments are now commercially available. Quantitative performance of such an instrument for routine use on industrial samples has been demonstrated. Results presented show success for the chemical mixtures used. Ruggedness, wavelength reproducibility, and cost make such equipment appropriate for near-IR quantitative analysis.
Software for automatic infrared spectroscopy of liquid samples: a new concept
Author(s):
Karl Molt;
G. Fischer
Show Abstract
Most modern FT-IR/NIR-Spectrometers fulfill the requirements for
automatic analysis in connection with autosaiuplers. Bidirectional
communication between a computer and the spectrometer is a common
feature. Sequences of application software commands for collecting
and evaluating spectra can be stored in macro files for later
automatic execution. Macro programming facilities often have some
of the advanced features of modern programming languages like
arithmetic calculations, loops, goto-statements, subroutines etc..
However for the design of complex automation systems macro
programming by itselve is not flexible enough e.g. for realizing
the input/output procedures or the logical flow of the automation
software. Additionally macro programming of large applications can
be very troublesome, complicated and time consuming.
We could provide additional flexibility for the solution of
complex automation tasks by designing a special compiler capable
of generating macro files. The compiler written in C gathers all
information needed for a certain batch of samples and generates a
suitable macro file. This macro file contains all commands for
driving the hardware (spectrometer and autosampler) and processing
the results. Several additonal service programs are responsible
for the user-interaction and the input/output of data.
