Intracavity UV-range laser spectrometer

We suggest a variant, which has already been implemented, of a selective intracavity laser spectrometer with intracavity nonlinear optical conversion of the frequency range of generated multimode radiation. The apparatus provides a means for transition into the UV spectral range (shorter than 300 nm) to carry out direct recording and quantative investigation of strong resonance lines of atomic absorption, which earlier were beyond the reach of the intracavity method. We measured selective absorption in spectral lines of a number of metals: FeI 296.690 nm, TiI 294.200 nm, and GaI 287.424 nm. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70 F. Skorina Ave., Minsk, 220072, Belarus; e-mail: Ild@imaph.bas-net.by. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 6, pp. 875–879, November–December, 1999.     

Recording of selective intracavity absorption at doubled frequencies of multimode laser radiation

We carried out measurements of the spectral distribution of wideband dye laser generation intensity within the limits and in the vicinity of an absorption line with its simultaneous recording at the frequencies of the fundamental and second harmonics of laser radiation. In the laser cavity we placed optical cuvettes with active and absorbing media, as well as selecting and nonlinear-optical elements. We show that at double frequencies the contrast of the narrow-band hole in the multimode laser generation spectrum increases. The gain in the concentration sensitivity of measurements depends in this case on the value of the absorption coefficient being determined. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., 220072, Minsk, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 516–521, July–August, 1998.     

Spectral-time characteristics of combined-target laser plasma

From the analysis of the contours of the spectral lines of target-material atoms, the electron and atomic concentrations and their variation with time are determined in the laser plasma of a combined Cu–Al–Cu target. The time dependences for the concentrations of electrons and atoms in the ground and excited states are explained within the framework of a model that allows for plasma decay being determined by processes of three-particle recombination and ionization as well as by the variation in the particle concentration in plasma expansion. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 426–432, May–June, 1998.     

Laser absorption and fluorescence diagnostics of a plasma

Diagnostics of a near-surface laser plasma, the plasma of a strong-current pulse gaseous discharge in inert gases, nitrogen, and carbon dioxide under conditions of intense evaporation of the wall of the discharge chamber, the plasma of a discharge with a hollow cathode, and the active medium of an excimer laser was conducted by methods of intracavity laser spectroscopy and laser-induced fluorescence. The dynamic fields and absolute concentrations of atoms, ions, molecules and electrons, the plasma temperature, and the velocities of flows of particles were measured. The quantitative determination of the density of particles in the erosion laser flame prior to breakdown and the phenomena associated with the formation of molecules in the laser plasma received primary consideration. To whom correspondence should be addressd. Instite of Molecular and Atomic Physics of the Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 281–290, May–June, 1997.     

Excited states, relaxation processes, and coordination reactions in the active centers of heme proteins

Based on the results of studying hemoglobin and myoglobin molecules using the methods of laser absorption spectroscopy of superhigh time resolution, we described photophysical and spectral properties of excited states, and intramolecular electronic and thermal relaxation processes. A mechanisms of the photodissociation reaction of oxy forms of these proteins is proposed and substantiated. Reported at the VIIIth International Conference on Spectroscopy of Porphyrins and Their Analogs, Minsk, September 22–26, 1998. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 479–482, July–August, 1999.     

Optical bistability of a thin layer of a substance with quasiresonance polarizability components

Optical-bistability conditions for a thin (smaller than the wavelength of the acting laser radiation) surface layer of resonance atoms are calculated with allowance for the influence of the polarizing fields of transitions adjacent to the resonance one and allowed in the electrodipole approximation on the transmissivity of the medium of the layer. It is noted that the change in the threshold bistability characteristics is due to the influence of the self-modulation broadening of the line of the laser field occurring in the thin resonancepolarized layer on the effective level of its absorption. Institute of Applied Optics, National Academy of Sciences of Belarus, 11, Byalynitskii-Birulya Str., Mogilev, 212793, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 5, pp. 661–665, September–October, 1999.     

Photoelectric properties ofp-CuInSe2 thin films obtained by pulsed laser vaporization

Using the method of phase-sensitive detection, we investigated the photoconductivity spectra of polycrystalline p-CuInSe₂ films obtained in vacuum by the method of pulsed laser vaporization of initial single crystals. We show that, in contrast to single crystals, films are characterized by monopolar photoconductivity in the extrinsic and intrinsic regions of optical absorption and by a linear mechanism of recombination of nonequilibrium charge carriers at the intensities of illumination 0–100 mW/cm² in the temperature range 80–300 K. Institute of the Solid-State and Semiconductor Physics, National Academy of Sciences of Belarus, 17, P. Brovka St., Minsk 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii. Vol. 66, No. 1, pp. 138–141, January–February, 1999.     

Determination of optical density at the center of an absorption line contour from the spacing between the frequencies of the two-component radiation spectrum of a laser having a phase-polarization selector

A method for determining optical density at the center of an atomic absorption line contour from the spacing between the components of the two-frequency generation spectrum of a laser with a phase-polarization selector is suggested. It is shown that the method makes it possible to measure the largest possible optical densities, but it is not suitable for measuring optical densities smaller than unity. Optical densities at the center of the D-lines of sodium are measured experimentally. A good agreement between experimental and predicted data is obtained. Institute of Molecular and Atomic Physics of the Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 738–743, November–December, 1997.     

“Gelios” compact atomic-absorption spectrometer with flame-free atomizer

The principle of operation and specifications of the “GELIOS” atomic-absorption spectrometer with a flame-free (tungsten) atomizer are described. Operation of the device under conditions of pulsed atomization and automatic control of the coil temperature is discussed. A distinctive feature of the device is use of a personal computer to control the coil temperature. Information on the software, test maintenance, reliability, and repairability of the spectrometer is provided. Belarusian State University, 4, F. Skorina Ave., Minsk, 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 604–607, July–August, 1998.     

Specific features of complete-absorption measurement in selective intracavity laser spectroscopy

For multimode pulsed dye lasers (of nanosecond and microsecond duration with frequency-dependent losses in the cavity), experimental studies and theoretical calculations have been made of the dependence of the value of the equivalent line width, used as a measure of selective absorption, on the main parameters characterizing the laser, the cavity, and the absorbent. Analytical relations have been obtained which describe the main aspects of complete absorption in lines with dispersion, Gaussian, or mixed spectra profiles, and their experimental testing has been carried out. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 3, pp. 327–332, May–June, 2000.     

Optoacoustic gas analyzer based on a13C16O2 laser for multicomponent pollution of air

A computer-aided optoacoustic gas analyzer based on a continuous¹³C¹⁶C₂ laser for multicomponent pollution of atmospheric air is described. The analyzer has the ability to detect absorption of radiation by detected substances at the level of ∼1·10⁻⁹ cm⁻¹ at a time resolution of 30 sec. Results of an experiment on simultaneous detection of H₂O, CO₂, NO₂, NH₃, HNO₃, OCS, and C₂H₄ in the atmospheric air using 40 laser lines are presented. B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 3, pp. 345–350, May–June, 1999.     

Remote detection of sulfur dioxide by means of a CO2 laser

The possibility of remote detection of SO₂ in the 9-μm region of the spectrum by means of a TEA CO₂ laser was theoretically and experimentally investigated with regard to the real state of the atmosphere and the contribution of background concentrations of H₂O, CO₂ and NH₃ to absorption. For sounding along short paths (2L=2 km), the method of detection of small concentrations of SO₂ (at the MPC level) with the use of the lines of the CO₂-molecule regular transitions (00^o1–02^o0 band) has been devised and experimentally tested. It is shown that in sounding along longer paths (2L=6 km), a noticeable increase in sensitivity can be achieved by the generation lines of the CO₂-molecule sequential 00^o2–02^o1 band. B. I. Stepanov Institute of Physics of the National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 508–515, July–August, 1998.     

Stability of the conditions for excitation of atomic spectra in plasma produced on exposure of copper alloys to laser radiation

We show that the temperature of plasma produced by exposure of copper-zinc alloy specimens to laser radiation changes little (within the limits of random errors) with a change in the conditions of the laser effect and chemical composition of the specimens. With use of electric discharges (a low-voltage spark), systematic changes in the temperature of the plasma are observed when the chemical composition of copper-zinc alloys changes. Institute of Molecular and Atomic Physics of the National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 319–321, May–June, 1998.     

Infrared multiphoton excitation of polyatomic molecules

Results of investigations of the process of multiphoton excitation of polyatomic molecules by CO₂-laser radiation are presented. The mechanism of formation of the profiles of IR absorption bands of polyatomic molecules is discussed. New experimental methods of investigation of relaxation processes at high levels of vibrational excitation of molecules in the ground and triplet states are considered. For vapors of polyatomic molecules and their mixtures with foreign gases, the quantitative characteristics of the collisional exchange and the vibrational-energy transfer as well as the rates of intercombinational conversion ⇛ and triplet-triplet transfer are presented and their dependences on the vibrational-excitation level are discussed. Institute of Molecular and Atomic Physics of the National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 5, pp. 675–693, September–October, 1998.     

Formation of chemical compounds in a laser plasma

Using the methods of laser-induced fluorescence and emissive spectroscopy, we carried out investigations of the formation of TiO molecules in a laser plasma produced by focusing the radiation of an AYG:Nd³⁺ laser on the surface of a titanium target in air. The radiation flux density varied within the range 10⁸–10¹⁰ W/cm². We investigated the distribution of molecules over internal states and the space-time distributions of Ti atoms in the ground, metastable, and excited states, as well as of TiO molecules in the ground and excited states. We found that gas-phase reactions with participation of Ti atoms in the ground state provide the most probable channel for the formation of TiO molecules; the role of reagents in ionized, excited, and metastable states is of secondary importance. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 109–115, January–February, 1999.     

Dissipation of laser-radiation energy in the gas surrounding a target in intense plasma formation

For the first time, the dissipation of laser-radiation energy in the gas surrounding a target is investigated under the conditions of intense plasma formation near a surface and the existence of large spots of: irradiation. The parameters of different regions of the heated gas are measured and an energy balance of the process of laser effects is obtained. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 814–817, November–December, 1998.     

Some characteristics of laser refractometric detection in a cylindrical cuvette

Results of sensitivity measurements in laser refractometric detection in a cylindrical cuvette are reported. A model of laser-beam transmission in a capillary with a liquid is developed. The influence of the laser-beam position, capillary and liquid characteristics, and laser power fluctuations on detection sensitivity is discussed. Institute of Molecular and Atomic Physics of the National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 894–899, November–December, 1998.     

Local spectral determination of gases and carbon in solid samples by the method of laser spectral analysis

We show the possibility of local spectral determination of nitrogen, oxygen, hydrogen, and carbon in solid materials with the use of a plasma obtained on exposure of materials to laser radiation, including single laser pulses. Institute of Molecular and Atomic Physics, National Academy of Sciences of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 482–485, July–August, 1998.     

Methods for fine-tuning frequencies of absorption of actinide complexes to frequencies of laser generation lines

On the basis of analysis of relationships relating, among themselves, the positions of bands in the spectra of electron and IR absorption of uranyl complexes in solutions and the donor ability of neutral ligands, the possibility is shown for fine-tuning frequencies of absorption of complexes to frequencies of argon- and CO₂-laser generation lines and using them in the development of methods of control over chemical reactions involving actinides. Belarusian State University, 4, F. Skorina Ave., Minsk, 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 3, pp. 420–422, May–June, 1999.     

Influence of isovalent substitutions on absorption spectra of orthoferrities

The role of impurity ions in formation of the optical properties of rare-earth orthoferrites is investigated. Optical spectra of the substituted against unsubstituted orthoferrites are presented. The influence of different isovalent substitutions on the optical absorption of orthoferrites that are promising for magnetooptics is studied. Institute of Solid-State and Semiconductor Physics of the Academy of Sciences of Belarus, 17, P. Brovka St., Minsk, 220072, Belarus. Translated from zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 5, pp. 642–645, September–October, 1997.