Proceedings Volume 4749

ICONO 2001: Novel Trends in Nonlinear Laser Spectroscopy and Optical Diagnostics and Lasers in Chemistry, Biophysics, and Biomedicine

Andrey Yuri Chikishev, Valentin A. Orlovich, Anatoly Nikolaevich Rubinov, et al.
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Proceedings Volume 4749

ICONO 2001: Novel Trends in Nonlinear Laser Spectroscopy and Optical Diagnostics and Lasers in Chemistry, Biophysics, and Biomedicine

Andrey Yuri Chikishev, Valentin A. Orlovich, Anatoly Nikolaevich Rubinov, et al.
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 30 May 2002
Contents: 2 Sessions, 52 Papers, 0 Presentations
Conference: XVII International Conference on Coherent and Nonlinear Optics (ICONO 2001) 2001
Volume Number: 4749

Table of Contents

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Table of Contents

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  • Novel trends in nonlinear laser spectroscopy and optical diagnostics
  • Lasers in chemsitry, biophysics, and biomedicine
Novel trends in nonlinear laser spectroscopy and optical diagnostics
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Femtosecond coherent Raman spectroscopy
Wolfgang Kiefer, T. Chen, M. Heid, et al.
Femtosecond time-resolved CARS spectroscopy is applied in order to prepare and monitor coherent states of different samples mainly in its electronic ground but also excited states. The time evolution prepared by such methods give information on the dynamics of molecular vibrations. In a first example, the fs CARS transients of iodine are investigated. Depending on the timing of the laser pulses different dynamics are reflected in the transient CARS signal. Second, we report on selective excitation of the vibrational modes in the electronic ground state of polymers of diacetylene by means of a femtosecond time-resolved CARS scheme. Control is achieved by varying the timing and the phase shape of the exciting laser pulses. Finally the electronic ground state dynamics of biologically relevant porphyrine molecules are studied with transient CARS spectroscopy.
Optimal coherent control of the molecular FWM response by arbitrarily shaped femtosecond pulses
Marcus Motzkus, T. Hornung, R. Meier, et al.
Coherent control of quantum phenomena can be achieved by using phase- and amplitude modulated laser pulses. With a self-learning loop, which combines a femtosecond pulse shaper, an optimization algorithm and an experimental feedback signal, it is possible to automatically steer the interaction between system and electric field. This approach allows control even without any knowledge of the Hamiltonian. We have successfully implement this learning loop for the coherent control of the nonresonant two-photon excitation in sodium. New solutions for 'bright' and 'dark' pulses could be designed for this two-photon resonance without previous knowledge of the resonances. In a further experiment we combined the self-learning loop with degenerate four-wave-mixing spectroscopy in order to study the influence of phase and amplitude modulated pulses on the molecular FWM response of the prototype system K2. The obtained control pulses typically show a complex structure which hides the responsible physical mechanism. In order to extract the applied mechanism the concept of parameterization has been introduced which allows the learning algorithm to optimize already known control processes. Therefore the control of vibrational wavepacket motion in the electronic ground and excited state could be attributed to chirped pulse excitation, impulsive Raman excitation by pulse trains and phase-related double pulses representing the well-known Tannor-Rice-Kosloff control scheme.
High-resolution spectroscopy of inhomogeneously broadened Raman resonances by time-domain CARS
V. G. Arakcheev, V. B. Morozov, A. N. Olenin, et al.
Time-domain technique was used for experimental investigation of narrow molecular resonances of H2 and CO2 with total width about 10-2-10-3 cm-1 and with spectral shape profile governed by several physical mechanisms. Experimental pulse response were measured in delay time range up to 16 ns. Qualitative and of numerical analysis of the results will be discussed.
Degenerate four-wave mixing and polarization spectroscopy in NO2
Degenerate Four Wave Mixing (DFWM) and polarization spectroscopy (PS) have been used to detect traces of nitric dioxide in a static cell at room temperature and in a small flame from a laboratory Bunsen burner. The high resolution spectrum of the Douglas-Huber band has been recorded with both techniques. The role played by population and thermal gratings in the DFWM case has been investigated under various experimental conditions. PS measurements performed with 'orientation' and 'alignment' configurations allowed to resolve NO2 composite spectral features.
Thermal mapping in a dry low NOx methane/air burner with N2 CARS spectroscopy
Michele Marrocco, Massimo D'Apice, Roberto Cipriani, et al.
The paper reports the measurements of thermal distributions inside a Dry Low Nox premixed combustor by using broadband Coherent Anti-Stokes Raman Spectroscopy in the planar BOXCARS configuration. Experimental spectra have been obtained for the main N2 vibrational lines and temperature determination was derived by means of a comparison with simulated nitrogen spectra at atmospheric pressure via a neural network analysis which permitted instantaneous temperature measurements.
Four-wave scattering by phonon polaritons under excitation of small polarons in LiNbO3:Mg
Galia Kh. Kitaeva, K. A. Kuznetsov, S. V. Solosin, et al.
We studied the coherent four-wave scattering of light by phonon polaritons in LiNbO3:Mg crystals before and after chemical reduction, which resulted in strong increase of small polarons. Large broadening of polariton lineshape was observed in a chemically reduced lithium niobate. To explain this effect we studied optical properties of LiNbO3:Mg in the visible and IR regions, where the undoped LiNbO3 was transparent. As a result, absorption band was found, being sensitive to the chemical reduction. We assign this band to the small polaron absorption. The values of polaron shift and the mean value of frequency of optical phonos, which interact with free electrons polaron formation, were measured. Influence of small polarons on polariton k-spectra was discussed.
Coherent four-wave mixing in hollow waveguides: expanding the possiblilities of gas-phase analysis
A. N. Naumov, F. Giammanco, Dmitri A. Sidorov-Biryukov, et al.
The influence of higher order waveguide modes on the process of coherent four-wave-mixing (FWM) in a gas-filled hollow fiber is studied for fibers with different inner diameters and different gas pressures. Higher order waveguide modes play an especially important role in FWM within the ranges of gas pressures where FWM processes involving such modes are phase matched due to the compensation of the gas dispersion by the dispersion of waveguide modes.
Three-wave Brillouin interaction in optical fiber
Vladimir A. Saetchnikov, Ellyn A. Chernyavskaya, Tatjana P. Yanukovich
Distributed temperature and train measurements can be realized by using stimulated Brillouin scattering. This effect can be described as a three-wave interaction of pump laser wave, a Stokes wave and an acoustic wave of characteristic Brillouin frequency. This frequency depends on temperature and strain. This effect is used for distributed measurements and realized in Brillouin optical time-domain analysis. In the method, the continuous wave light of narrow linewidth pump laser is coupled into one end of the sensor fiber and a sinusoidal modulated intensity of a probe laser is coupled to the other end. If the frequency difference between both lasers equals to characteristic Brillouin frequency, the pump light will interact with the modulated probe light in the fiber. By analyzing the transmitted pump intensity at different frequency differences between probe and pump lasers, the temperature and strain distribution along the fiber can be determined. In this numerical simulation several fiber lengths with different but spatial constant gain coefficients were placed one after another. For each fiber part the fundamental oscillation of the transmitted pump intensity is calculated by the derived analytical expression with respect to individual Brillouin gain coefficients. The DC components of the input pump and stokes powers of each region are determined by numerical iteration. Only the DC component of the pump power produces Brillouin interaction. Considering the phase shift of the transmitted alternating components of the pump powers of each different located fiber regions, the baseband modulation transfer function is calculated. By means of inverse Fourier transformation pulse response is calculated. Pulse response is a 2D function of length of fiber and frequency difference between probe and pump lasers. It gains maximum when frequency difference is correspondent to characteristic Brillouin frequency of certain temperature and strain. So, pulse response represent distribution of temperature and strain along optic fiber.
Four-photon Raman spectroscopy as a method of ocean remote sensing
A. F. Bunkin, Konstantin I. Voliak
Applicability of four-photon spectroscopy to remote sensing of the ocean is considered. It is shown that the advantages of nonlinear spectroscopy, such as the high level of the recorded signal, enhanced spatial and time resolutions, are realized in remote sensing. Experimental results on detecting of hydrocarbons in water are presented.
Time-resolved polarization-sensitive measurements of the electric field in a sliding discharge by means of dc-field-induced coherent Raman scattering
S. N. Tskhai, D. A. Akimov, S. V. Mitko, et al.
We investigate the properties of the IR signal generated through coherent Raman scattering involving the Q(1) transition of a hydrogen molecule in the presence of the quasi-static electric field of the sliding discharge propagating along a ferrite surface in a hydrogen atmosphere. The results of time-resolved polarization- sensitive measurements performed on this signal are employed to determine the parameters of the electric field in the sliding discharge. These measurements have shown, in particular, that the propagation of the discharge leader along the ferrite surface is accompanied by the rotation of the vector of the quasi-static electric field.
Strong-field theory of polarization sensitive spectroscopy
Igor I. Gancheryonok, Oleg Gennadievich Romanov, Alexei L. Tolstik, et al.
We report new theoretical results on polarization effects within pump-probe scheme of interaction in polarization inhomogeneous media. Our findings are applicable to explanation of experimental data on combustion diagnostics as well as for optimization of polarization geometry conditions under saturation regime.
Three-dimensional microimaging of inhomogeneities in transparent media using third-harmonic generation and four-wave mixing
D. A. Akimov, Stanislav O. Konorov, Dmitri A. Sidorov-Biryukov, et al.
Third-harmonic generation and four-wave mixing processes are shown to allow inhomogeneities in spatial distributions of absorption, refractive index, and nonlinear susceptibility to be imaged, thus offering a convenient method of 3D microimaging.
Microscopic imaging of semiconductor surfaces and interfaces
Vladislav V. Yakovlev, Katerina Mikhailichenko, Sergei V. Govorkov
We propose and experimentally demonstrate two spectroscopic techniques for microscopic imaging of water stains on the surface of semiconductors and crystal structure of the surface layers.
Linear and quadratic Stark effect studies of the Cs ground state using Faraday-Ramsey spectroscopy
Ulrich Rasbach, Christian Ospelkaus, Antoine Weis
Spin alignment created by optical pumping with linearly polarized resonance radiation in a thermal beam of cesium atoms is allowed to evolve in static electric and/or magnetic fields over a distance of 30 cm and is probed downstream via the paramagnetic Faraday rotation. When scanning the applied fields typical Ramsey fringes are obtained, although no oscillating fields are used. With a suitably chosen field geometry one observes a linear Stark effect, which may be interpreted in terms of the Aharonov- Casher phase shift and which allows to calibrate the electric field. In another geometry the technique can be used to measure the electric tensor polarizability of the Cs ground state. This polarizability is suppressed by 6 or 7 orders of magnitude with respect to the scalar polarizability. The measurement is expected to shine more light on a long standing discrepancy between theory and experiment.
Methods of laser spectroscopy on the forbidden 21S-23S transition of helium
E. V. Baklanov, A. V. Konovalov
Two methods of laser spectroscopy for the forbidden 21S- 23S transition of helium atom are considered: the resonance absorption and the stimulated Raman scattering. Analysis made has shown that the measurement of the 21S- 23S transition frequency of helium atom with an accuracy 1 kHz is possible.
Single-molecule spectroscopy of molecules isolated in solid-deposited matrices
A. S. Starukhin, Alexander M. Shulga, Valentin N. Knyukshto, et al.
In this work we report the spectroscopic observation of single organic molecules in solid-deposited matrices using a confocal microscope at liquid-helium temperature. The fluorescence microscopy allowed to study the spectroscopic properties of many single molecules in parallel Matrix isolation technique was adopted to produce a solid samples directly on the objective surface. From sequential images recorded at different excitation laser frequency the spectral line-widths of corresponding zero-phonon absorption lines could be obtained. For investigated compounds of interest at different matrices the line-widths have been measured. Spectral stability of single molecules has been investigated under excitation.
Spectroscopy of coherent dark resonances in samarium
J. V. Vladimirova, Boris A. Grishanin, Victor N. Zadkov, et al.
A theoretical model of the coherent population trapping (CPT) in multilevel samarium atom and its comparison with experimental spectroscopic data are presented. Theoretical model describes a degenerated (Lambda) -system in Sm atom formed of the transitions 4f66s2(7F0) mutually implies 4f6(7F)6s6p(3Po)9Fo1 mutually implies 4f66s2(7F1) and includes also a fourth level 4f66s2(7F2), which complements the model making it an open system. An open character of the system reduces the contrast of the resonance curves in the CPT- spectra, but does not change the width of the CPT resonance. Numerical modeling of the CPT resonances in Sm atom was carried out for the case of applied longitudinal and transverse magnetic fields in 7- and 12-level models, as well.
New opportunities in solution of inverse problems in laser spectroscopy due to application of artificial neural networks
I. V. Gerdova, I. V. Churina, S. A. Dolenko, et al.
Inverse problems in laser spectroscopy are reported to be successfully solved by application of artificial neural networks, a powerful data processing technique that performs better than traditional variation algorithms of solving inverse problems.
Laser hypersound spectroscopy in Si and GaAs
N. V. Chigarev, Dmitri Yu. Paraschuk
We apply a transient pump-probe photo deflection technique to measure the profiles of subnanosecond sound photoexcitation. We show that the photoexcited electron-hole plasma expands with a supersonic velocity in GaAs and a subsonic velocity in Si.
Data processing and estimation of measurement errors in intracavity laser spectroscopy
Victor S. Burakov, Vladimir V. Apanasovich, A. V. Isaevich, et al.
Methods of absorption spectra processing in intracavity laser spectroscopy are investigated for the case of very low quantities of cesium in water solutions. Common procedures in such case require fitting or filtering of the laser generation broadband spectrum, search for the investigated atomic or molecular absorption lines, calculating the examined substance concentration in qualitative analysis or its state determination in quality analysis. In this study various methods of absorption spectra processing in the case of atomic cesium line (lambda) equals 455.531 nm in the intracavity laser spectrometer are examined. Methods based on digital filtering and approximation were tested. The artificial neural network algorithm was tired as a tool to reduce the apparatus error. For the trace concentration definition the mean-square error was decreased to a value less than 9 percent.
Nonlinear optical diagnostics of hydrogen emission process from dielectric oil
Gennady M. Mikheev, Georgi M. Mikheev, Aleksandr N. Kulikov, et al.
Hydrogen emission processes from transformer oil under the electrical breakdown and low power ultrasonic where investigated by the method of coherent anti-Stokes Raman scattering. It was shown that low power of ultrasonic may be successfully used for degassing of transformer oil. The diffusion coefficient of hydrogen in transformer oil was measured.
Photoinduced electronic processes on second-harmonic generation at reflection from a silicon surface: transversal Dember's effect
I. M. Baranova, K N. Evtyukhov, A. N. Muravyev
The electronic processes stimulated by laser pulses in an internal part of the weakly absorbing semiconductor (SC) are theoretically investigated. The physical and mathematical model of diffusive-drift and relaxational electronic processes called by infinite sequence of nanosecond laser pulses is offered. It is shown, that a consequent of these processes is the transversal Dember's effect - originating of a radial field both potential differences between lighted and unlighted parts of a volume of the SC. The calculation show, that in silicon the transversal Dember's potential difference is commensurable with representative values of a surface potential and, therefore, plays an essential role in nonlinear - optical processes on a surface of the SC.
UV tunable diode laser source based on an external resonant cavity for OH absorption detection
J. S. Gibb, G. Hancock, Vasily L. Kasyutich, et al.
A solid-state tunable light source operating at 309-320 nm has been developed based on frequency up conversion of a cooled diode laser. Frequency doubling is achieved with a beta barium borate crystal enclosed in an external bow-tie cavity. The radiation produced is used for absorption detection of hydroxyl radicals generated by microwave discharge. The ultra-violet beam can be scanned 20-30 Ghz by tuning the length of the doubling cavity using a piezoelectric transducer on one of the mirrors and locking the diode laser to the bow-tie cavity. Possible applications of the developed system to the hydroxyl radical detection in atmospheric and chemical dynamics research are discussed.
Coherent and optical methods of the diagnostics of periodic structures with the increasing sensitivity of measurements
A. M. Lyalikov, M. Yu. Serenko
The methods of visualization of both various defects of periodic structures and surface shape of periodic objects are considered. Experimental verification of the methods in the investigating of various transparent periodic objects is presented.
Lasers in chemsitry, biophysics, and biomedicine
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Application of gradient laser fields in biology and medicine: physical principles and prospects
Anatoly Nikolaevich Rubinov, Anatoly A. Afanas'ev
In 1986 Ashkin and coworkers have for the first time demonstrated the trapping of microparticles by a sharply focused laser beam [1]. Since then the optical tweezers have be- come indispensable tool for selective capture and translation of dielectric microparticles. The tool proved to be especially efficient in biological studies. Biological objects such as cells or cell organelles as well as small probes inside a cell can be held and moved by exertion of forces as low as several piconewtons without damaging the cell. A vast number of biological applications, such as micromanipulation of viruses and bacteria [2], quantitative measure- ments of forces in molecular motors [3-7], induced cell fusion [8], tweezing and cutting in immunology and molecular genetics [9,10], chromosome movement [1 1], motility of human spermatozoa [12], mobility of transmembrane proteins [13,14], mechanics of kinesin mole- cules [15], and others have been successfully demonstrated. Mechanism of particle trapping in laser tweezers is based on the influence of light pressure and dipole gradient forces on a particle in a strongly focused light beam. The theory of the interaction of a microparticle with a focused light beam and methods of calculating trapping forces have been presented in a number of publications [16-23]. At the same time more general problem — the interaction of spatially modulated light fields with ensemble of particles in liquid and the possible influence of such fields on the on functioning biological systems, in particular, human organism — remains unexplored. In this paper we are discussing the possible effects of spatially modulated laser light at nonresonance interaction with heterogeneous media, including biological objects. In particular we are frying to show that, contrary to popular beliefs, the effect of the highly coherent laser radiation on biological structures, and on the living organism as a whole, can differ radically from that of incoherent radiation with the same intensity, duration, and wavelength. The main difference between coherent and incoherent illumination is the formation of speckles in the first case. Upon illumination of heterogeneous medium by laser radiation, a speckle structure of light field is created both on a surface and in a bulk of the body due to the interference of scattered components with each other and with the incident light beam. This structure is charrn acterized by a sharp small-scale spatial modulation ofradiation intensity, i.e. by strong spatial gradients ofthe light field. Apart from the speckles, which appear in a body automatically, the gradient laser field may be created artificially by using interference of laser beams. It allows to obtain one-, two-, or three-dimensional modulation of radiation intensity with the controllable spatial period across a biological object. Interaction of such spatially modulated laser fields with heteroge— neous system will be accompanied with the local action of gradient forces. Basically the gra— client forces can cause two effects: 1) change of the local concentration of certain biological components of a micrometer-scale (enzymes, erythrocytes, leukocytes, etc.) and 2) stimulation of conformational changes in various biological structures both within the cell and on the supracellular level. As a result, this can lead to changes in the character of the cell metabolism, and possibly to changes of its genetic properties. First we shall discuss the physics of gradient laser fields interaction with particles and then very briefly their possible applications in biology.
Photodynamic laser therapy in the transparency region of biotissues using tricarbocyanine dyes as photosensitizers
Eugene S. Voropay, Michael Petrovitch Samtsov, Anatoliy P. Lugovsky, et al.
Investigation of the spectral properties of polymethine dyes in organic solvents, water, nutritious media and cell cultures at various concentrations has demonstrated that the tumor cells contain monomers of the dye molecules. Pharmacokinetics of the different dyes has been studied both in vivo and in vitro. After incubation of a cell culture in the presence of a nontoxic does of the dyes their concentration in tumor cells is rather high, varying for different preparations from 10-11 2.1 10-9 mol per million cells. The biggest phototoxicity in vitro has been observed for polymethine dyes with indolenine end groups. In vivo concentration of the dyes in tumor tissues was higher than in normal muscle tissues ranging from 1.2 to 3.6 for different kinds of tumor. Photo bleaching of dyes during photodynamic treatment was observed. The photodynamic treatment with some polymethine dyes caused tumor tissue necrosis up to 20 mm in depth.
Visualization of intracellular Ca2+ dynamics with third-harmonic generation microscopy
R. Barille, S. Rivet, Lionel Canioni, et al.
Measurements by Laser scanning Third Harmonic Generation microscopy of Ca2+ dynamic release from internal stores and/or calcium influx in biological cells is presented. The Ca2+ signal consists of a transient increase in the intracellular concentration. A good correlation is found between these measurements and measurements done with microspectrofluorometry.
Selective destruction of viral particles capsides by powerful laser radiation
A. A. Manykin, N. B. Matsko, N. N. Gabishev, et al.
Powerful laser radiation was applied to destroy capsides of viral particles in order to study the internal DNA organization. The significant results were obtained for bacteriophage Phi KZ. The possible mechanisms of capside destruction were considered.
Laser detoxication of acute poisonings with carbon monoxide
Alexander Sergeevich Provorov, Vladimir V. Salmin, Ekaterina Yu. Stavitskaya, et al.
A series of model experiments have been carried out. Those experiments have proved the fact of laser-induced photo dissociation of HbCO using Nd:YAG-laser with wavelength 533 nm at different conditions. Spontaneous reassociation of ligand to hemoproteid has been observed during the interpulse period. In order to prevent the reversibility of the reaction some oxidizing substances as well as trap-like functioning agents have been tested. The preliminary results allow us to propose the application of nonreversible laser- induced HbCO photodissotiation in the capacity of new physical method to treat acute carbon monoxide poisoning.
UV-induced signal transduction in epidermal cells: from surface receptors to protein kinase C (a mathematical model)
Mikhail M. Stolnitz, Anna Yu. Peshkova
In the paper the mathematical model of UV-induced PKC activation is presented. Phosphorylation of membrane receptors, activation of phospholipases and phospholipids turnover, diacylglycerol, inositol trisphosphate and arachidonic acid production, calcium releasing are taken into account.
Interactions of new derivatives of anthracene with calf thymus DNA
Marian Wolszczak, Edyta Grzesiak, Dorota Kowalczyk, et al.
A series of anthracenes and bis-anthracenes have been subjected to photophysical study in water and in solutions of calf thymus DNA. The DNA binding properties have been studied using absorption, emission, melting DNA, viscometric and fluorescence polarization experiments. These studies indicate intercalation of anthryl probes into DNA helix. Trifunctional molecules consisting of two antrhacenes linked bya polyamine chain intercalate into DNA with binding constants in the range 2 × 104 - 8 × 105 M-1 depending on the linker properties. In the homogeneous solution the fluorescence of anthracene moieties shows the mono-exponential decay, with a life-time of about 8-9 ns. Upon binding to DNA, the fluorescence of anthryl probes is strongly quenched by the DNA bases. Furthermore, the fluorescence decay profile shows a distinct bi- exponential behavior in the presence of DNA with a short- lived component of 8 ns and with dominating long-lived component of 30 ns. The anthryl triplet decay kinetics is also altered by the presence of the polynucleotides. On the one hand the yield of the triplet is dramatically decreased, and on the other hand the life-time of the triplet is increased in the DNA solution. The reaction of the aquated electron with intercalculators has been investigated by pulse radio lysis technique in water and in the presence of DNA. The rate of reaction of eaq- with intercalated anthracenes is reduced tenfold in respect to that for free molecules. While direct scavenging of eaq- with intercalated anthracenes is reduced tenfold in respect to that for free molecules. While direct scavenging of eaq- by the anthracenes intercalated into DNA was observed, electron migration form DNA base radical anion to the intercalator was not.
Multiple light scattering by suspensions of erythrocytes in geometrical optics approximation
Vladimir V. Lopatin, Alexander V. Priezzhev
New method of intensity calculation of multiple light scattering by suspensions of large nonspherical particles is developed on the basis of geometrical optics approximation. As an example of application of the method the calculation of light scattering by a suspension of aggregating particles modeling the kinetics of erythrocyte aggregation in whole blood is executed. The size of aggregates changes in the aggregation process. Light scattering indicatrices for deformable particles moving in shear flow are calculated. Theoretical explanation of experimentally observed phenomenon of light scattering asymmetry is given by analyzing the shapes of scattering indicatrices, and the theoretical time dependence of the backscattered intensity is obtained.
Neoplasm diagnostics based on fluorescence of polymethine dyes
Michael Petrovitch Samtsov, Eugene S. Voropay, Vadim N. Chalov, et al.
Investigated polymethine dye TICS has near IR bands of fluorescence and absorption within the transparency region of biological tissues. It can be detected up to 1.5 cm from the surface of the skin. The intensity of a fluorescence signal of TICS is linear for doses up to 2 mg/kg in both tumor and muscle tissue. The ratio of an intensity of light induced fluorescence in tumor tissue to one in muscle tissue is up to 3.6 for rapidly growing tumors. The retention time of TICS is 7 days in all tissues. TICS can be used in the detection of tumor boundaries and tumor internal structure.
Fast visualization of internal structure of multiple-scattering objects by diffusion optical tomography
Fast approximate statistical nonlinear algorithm of the diffusion optical tomography inverse problem solution has been described. Results of this algorithm approbation by the example of reconstruction of a rather complicated internal structure of strongly scattering and weekly absorbing large- size model objects have been presented. CW radiation of low- power diode lasers of near IR region has been used in experimental realizations.
Opto-acoustic measurement of optical properties of turbid media
Alexander A. Karabutov, Natalia B. Podymova, Ivan M. Pelivanov, et al.
Time-resolved laser optoacoustic method was developed for the measurement of the spatial distribution of laser fluence rate in uniformly absorbing and scattering condensed turbid media and to determine the optical properties of such media - effective light attenuation and absorption coefficients. This method is based on detection of laser-induced acoustic transients in an investigated medium with high temporal resolution. The effective light attenuation coefficient is measured by exponential fitting of the front of optoacoustic transient. To determine the light absorption coefficient we investigated features of the spatial distribution of laser fluence rate beneath the surface of an irradiated medium. We proved both experimentally and with Monte-Carlo simulation, that the location of the maximum of laser fluence rate distribution in a turbid medium depends solely on the ratio of light absorption and effective light attenuation coefficients, if the anisotropy factor of light scattering is higher than 0.8. This dependence can be employed to calculate the light absorption coefficient of turbid media from the leading edge of laser-excited optoacoustic transients.
Optimizing optical imaging of tumor-like inclusions in biological tissues
Vladimir V. Barun, Alphiya Ya. Khairullina
We use the diffusion approximation to the radiative transfer equation and the respective analytical relations to theoretically treat the imaging of phantom biological tissue with an inclusion under external illumination. The horizontal inhomogeneity of the scattering and absorbing tissue medium owing to the includion is taken into account. Several measuring setups are computationally considered to investigate their advantages and drawbacks under the sounding of inclusions by reflected and transmitted light. We varied the absolute and respective values of the absorption coefficients of the inclusion and surrounding tissue to illustrate the imaging of 'clear' and 'dark' inclusions through the turbid medium. The comparison is made with the so-called base scheme when an arrow laser bam illuminates the medium and narrow-angle receiver records reflected radiation at some distance or base from the light source. A simple formula to calculate the image contrast of a small inclusion with the contrast observed. We illustrate the computations by experimental spectral absorption and extinction curves to enable one an opportunity to estimate some advantages while searching and changing the operational range of wavelengths utilized to sound a tumor inside normal tissue.
Laser-induced photochemical gas-phase reactions of vibrationally excited triplet molecules
G. A. Zalesskaya, D. L. Yakovlev, E. G. Sambor
Mechanisms and rates of laser-induced gas-phase reactions of vibrationally excited triplet ketones were studied after adding electron and hydrogen donors using time-resolved delayed fluorescence. The influence of various bimolecular competing processes on DF quenching was analyzed.
Ultrafast chemical dynamics by intense-laser field dissociative ionization
S. A. Trushin, Werner Fuss, K. K. Pushpa, et al.
When investigating photochemical dynamics, one usually measures the time for disappearance of the primary excited state or the appearance of the product state or the total time the molecule needs for traveling from the former to the latter. Quantum chemistry predicts, however, that molecules often pas on this way via intermediate potential energy surfaces and conical intersections, the path sometimes branching and changing direction. In the conventional methods this intermediate region remains in the dark. We show that probing by intense-laser field ionization and mass-selective detection provides surprisingly many time constants which can reveal this region and thus practically allow to 'look into the black box', it is thus possible to monitor the molecule's pathway all along the potential energy surfaces from the initially excited region down to the ground state of the product. Even driving forces can be recognized. We discuss these and other advantages, but also pitfalls of this method and compare it with other methods of probing.
Solvate shell microstructure of dye molecules in water-organic binary solvents revealed by polarization picosecond laser spectroscopy
Boris A. Bushuk, Anatoly Nikolaevich Rubinov, Yu. Kalvinkovskaya, et al.
The microstructure of Rhodamine 6G solvate shell in binary water-organic solvent is investigated by means of steady- state and picosecond spectroscopy. The participation of intermolecular solvent-solvent H-bond in solvate shell formation is established.
Dynamics of molecular exchange-resonance photoprocesses on the surface of chemically modified silica
V. V. Bryukhanov, I. G. Samoussev
The photoprocesses with organic lumenophors adsorbed on the surface of broad-porous silica chemically modified by n- alkyl hydrocarbons after laser photoexcitation are considered. The results obtained are interpreted in terms of the exchange-resonance processes of triplet-triplet energy transfer acceleration diffusion model along with homo- and hetero-triplet-triplet annihilation of the interacting molecules.
Kinetics of photobleaching of aqueous solutions of ricin agglutinin in the presence of guanidine chloride
Nikolai N. Brandt, Andrey Yuri Chikishev
Kinetics of background decay in Raman spectra of aqueous solutions of ricin agglutinin in the presence of guanidine chloride were measured. The differences in the kinetics of photobleaching are discussed.
Background photobleaching in raman spectra of aqueous solutions of plant toxins
Nikolai N. Brandt, Andrey Yuri Chikishev, Alexander G. Tonevitsky
Kinetics of background photobleaching in Raman spectra of aqueous solutions of ricin, ricin agglutinin and ricin binding subunit were measured. It was found that the spectrum of Raman background changes upon laser irradiation. Background intensity is lower for the samples with lower molecular weight. Photobleaching is characterized by oscillations in the multi exponentially decaying intensity.
Kinetic description of dioxygen binding to human hemoglobin on the 1-100 ns time scale
I. V. Sazanovich, Vladimir A. Galievsky, J. Karpiuk, et al.
The results of nanosecond optical spectroscopy studies of hemoglobin geminate recombination on the 1-100 ns time scale are presented. Analysis of transient absorption data has shown that (i) the kinetics of O2 recombination to hemoglobin cannot be described as a single-exponential process, and (ii) the predominant part of geminate recombination takes place on the initial stage of this process. The analysis pattern as two exponentials and background yields two processes occurring during the geminate recombination on the 1-100 ns time scale having the time constants of 1.2 +/- 0.2 ns and 16 +/- 2 ns. However, the signal-to-noise ratio of the data does not allow to make an unambiguous between several possible non-exponential decay models.
Extra-ligation and screening effects upon interaction of photoinduced excited states of multiporphyrin arrays with molecular oxygen in solutions
Eduard I. Zenkevich, E. I. Sagun, Valentin N. Knyukshto, et al.
In this work we present the results showing how the extra-ligation, spacer properties and porphyrin macrocycle screening may influence on the conformational dynamics and photophysical properties of multiporphyrin arrays as well as on their interaction with molecular oxygen in solutions at 293 K. Steady-state and time-resolved studies indicate that for a sequence of porphyrin or chlorin chemical dimers Zn- cyclodimer yields (ZnOEP)2Ph yields (ZnOEP)2 yields (ZnOEChl)2 with relative lowering of excited S1- and T1-states, the extra-ligation by pyridine does not influence essentially on fluorescence parameters but leads to an increase of T1-states non-radiative decay. At 293 K the T1-state quenching by O2 for Zn-dimer- pyridine complexes depends on the nature and flexibility of the spacer between macrocycles and donor-acceptor interactions with pyridine. In triads and pentads the dimeric subunit plays the role of screen weakening O2 interaction with the second subunit. As a result, the T1-state quenching by O2 in triads and pentads is decreased by 50 divided by 70 percent with respect to that for the corresponding individual monomers.
Laser-induced polarization rotation effect in solutions of the glycine
S. A. Bakhramov, E. V. Vaganov, A. M. Kokhkharov, et al.
The laser induced nonlinear polarization rotation effect in a solution of Glycine has been investigated. The experimental data on polarization rotation of the laser beam are presented and have been used to determine of the third- order molecular susceptibility for the process of interest.
Photochemistry of pyrylium compounds: excitation-induced rearrangement of a molecule-solvent complex
E. N. Kaliteevskaya, V. P. Krutyakova, T. K. Razumova, et al.
Photochemical rearrangement of the complex pyrylium molecule - solvent is studied in solvents of various polarity and nucleophilicity. Upon photoexcitation two types of transient fluorescent excited-state complexes are formed due to intramolecular charge transfer and geometrical rearrangement of the complex.
Laser photomodification of nucleic acids by xhantene dyes
S. N. Letuta, Y. D. Lantukh, S. N. Pashkevitch, et al.
Various ways of photomodification of nucleic acids by laser radiation of a visible range are considered in the work The molecules of xhantene dyes participate in all cases of modification. Dye acts as a mediator between laser radiation and macromolecule.
Peculiarities of dynamics of molecular multilevel systems in a powerful laser field: anaytical solutions
V. A. Savva, V. Zelenkov, O. V. Khlus
Analytical solutions of the equations describing coherent dynamics of various multilevel systems excited by radiation are given. The peculiarities of dynamics related with detuning from resonance, with arrangement and amount of levels, with dipole moment dependence on level number, along with excitation in a pulse laser field are studied.
Determination of the photosynthesizing organisms photophysical parameters by the method of nonlinear fluorimetry
Viktor V. Fadeev, D. V. Maslov, P. N. Litvinov, et al.
There is a set of discussed questions in the study of primary processes of the photosynthesis. Solution of these problems stimulates development of new methods for determination of the photo synthetic unit photo physical parameters in-vivo. In the report possibilities of non- linear fluorimetry method in this problem are investigated. The first step requires creation of low-parametrical model of the photosynthesizing organisms fluorescence response formation. The corresponding inverse rpobe4lm can be solved for this model.
Collective librations in the LH2 antenna systems and modulated broadening of B800 and B850 absorption spectra
Vladimir S. Pavlovich
The collective librations of the linked polar fragments and polar elements in the LH2 antenna complex and in the protein environment of the photosynthetic purple bacteria are described as a motion of the histons, new quasi-particles. Assuming that the exciton-phonon coupling is fairly weak, we study the effect of the dynamic disorder on the B800 and B850 absorption spectra as a result of the exciton-histon interactions. Taking into account that the histons modulate the frequency of exciton transitions, the mean-square thermal fluctuation of the frequency and the half-width of absorption spectra have been defined as a function of the difference in permanent dipole moment between excited and ground states. Theory is used for interpretation of the well-known experimental data on thermal broadening of the B800 for LH2 of Rb. Sphaeroides and Rps. Acidophila in the glycerol-water solvent. In the calculations it is suggested that the effects of static disorder are enchanged under these temperature conditions. Obtained equation for the full half-width provides an excellent fit to the Rb. Sphaeroides and Rps. Acidophila B800 known data at 4.2-270 K with an average histon frequency of 63 and 50 cm-1, respectively. The reasons of large distinction of the zero- phonon hole half-widths at the laser burn wavelengths near the B800 and B850 maxima are also briefly discussed.
Red-edge excitation effect in intramolecular proton transfer in flavonols
Julia V. Kruchenok, Nicolai A. Nemkovich, A. N. Sobchuk, et al.
To investigate of 4'-diethylamino (FET) and 4'-(15-azacrown- 5) (FCR) derivatives of 3-hydroxyflavone in binary solvents and erythrocyte ghosts, we used the red-edge excitation spectroscopy. The results obtained prove the existence of spectral heterogeneity of flavonols in the studied systems. The effect manifests itself in the dependence of the efficiency of excited-state intramolecular proton transfer on the excitation frequency.
Concentration quenching of photoinduced activity of bacteria in the processes of triplet excited states and mechanisms of their deactivation
Alexandr Evganyevic Obukhov, Eugeny Ph. Stranadko
A series of experimental studies on lethal photosensitization of microorganisms most often met in suppurative wounds were carried out. The reason lies in the fact that the processes of reabsorption of energy of excitation are of two-photon nature; generally, the photochemical processes are multiphoton and are followed by recombination of the charged particles in the active medium.