dispersion of induced amplitude and phase anisotropy of viscous solutions of dyes

Studies are conducted to investigate changes in the state of polarization of probing radiation that passed through anisotropically excited solutions of rhodamine 6G and 3,6-tetramethyldiamino-N-methylphthalimide in glycerin. The studies allowed the authors to find characteristics of spectral behavior of amplitude and phase anisotropy in these systems. A qualitative difference is found between the spectral behavior of differences in the refractive indices Δn-n_y−n_Z of these solutions simulated by different systems of energy levels of active molecules. Institute of Molecular and Atomic Physics of the National Academy of Sciences, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 486–490, July–August, 1998.     

Evaluation of refractive index of cylindrical microlenses from spatial distribution of interference orders

An interference method for measuring the refractive index and surface curvature of cylindrical microlenses is considered. The method consists in probing microlenses by a dynamic interference pattern with a localization of order of several to tens micrometers corresponding to the period of the interference fringes. Basic analytical expressions for evaluation of the curvature radius and refractive index of the probed portion of the microlens are presented. Institute of Electronics, Academy of Sciences of Belarus, 22, Logoiskii Trakt, Minsk, 220841, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 390–395, May–June, 1997.     

Color and optical characteristics of carbon coatings produced by magnetron sputtering

The color parameters of carbon coatings deposited by magnetron sputtering of a graphite target onto substrates of stainless steel without a sublayer and with a titanium sublayer are calculated. By numerical modeling, the refractive indices and extinction coefficients for the titanium sublayer and carboniferous film as well as the volume content of titanium dioxide in the sublayer are determined. Physico-Technical Institute of the Academy of Sciences of Belarus, 4, Zhodinskaya St., Minsk, 220141, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 374–385, May–June, 1997.     

Effect of sweeping the “instantaneous” lasing frequency on the amplitude-detuning characteristic of a CO2 laser with loss modulation

The influence of changes in the refractive indices of the active medium and the loss modulator on the amplitude-detuning characteristic of a CO₂ laser was theoretically investigated. It is shown that at a comparatively great magnitude of sweeping the “instantaneous” lasing frequency, the magnitude of the laser response increases not only in negative detunings, but also over a wide range of positive detunings. The use of the procedure of changing the magnitude and sign of detuning as well as the range of sweeping and the frequency of modulation makes it possible to realize various periodic and chaotic regimes of lasing, i.e., to exercise control over the time and energy parameters of pulses over a very wide range. B. I. Stepanov Institute of 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. 318–324, May–June, 1997.     

Investigation of the Raman spectra of CuxAgl−xGaS2 solid solutions

Raman spectra in (┴, ┴) and (║, ║) polarizations are investigated on crystals of CuGaS₂, AgGaS₂ compounds and Cu_xAg_l−xGaS₂ solid solutions. The frequencies of longitudinal and transverse optical phonons are determined, their concentration dependences are constructed, and the behavior of the vibrational modes in Cu_xAg_l−xGaS₂ solid solutions is established. Belarusian State University of Information Science and Radioelectronics, 6P, Brovka St., 220069, Minsk, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 447–449, May–June. 1998.     

Vibrational spectra of CuAl x Ga1−x S2 solid solutions

Investigations of the IR reflection and Raman spectra in polarized light are carried out on single crystals of the ternary compounds CuAlS₂ and CuGaS₂ and solid solutions based on them grown by the method of chemical transport reactions. The frequencies of longitudinal and transverse phonons are determined, the IR intensities and damping factors of phonons (ε₀, ε_∞) are calculated, and their concentration dependences are constructed. It is established that optical vibrations in the solid solutions manifest a mixed behavior. Belarusian State University of Information Science and Radioelectronics 6 P. Brovka Str., Minsk, 220072, Belarus; e-mail: kafchim@gw.bsuir.unibel.by. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 6, pp. 800–803, November–December, 1999.     

Laser-Radiation-Induced Optical Anisotropy of Rhodamine Dye Solutions

We have made spectral studies of induced optical anisotropy (its quantitative measure is the difference of refractive indices of the ordinary and extraordinary beams n = n _o – n _e) of Rhodamine 6G and 4C solutions in glycerol upon excitation in the UV region of the absorption spectrum. The observed spectral dependences of n of the above dye solutions excited in the UV (short-wavelength) and visible (long-wavelength) regions of the absorption spectrum are explained from the point of view of the molecular model. The proposed methods for investigating induced optical anisotropy of solutions of organic compounds make it possible to reliably determine the relative orientation of molecular electronic oscillators in the molecule skeleton and, consequently, the mutual orientation of the dipole moments of transitions.     

Parametric generation of light in arbitrary directions of a biaxial KTP crystal pumped by an Nd:YAG laser

The conditions for collinear phase matching in the parametric generation of light in arbitrary directions of a biaxial KTP crystal pumped by an Nd:YAG laser were investigated with the use of invariant expressions for the refractive indices of isonormal waves. The tuning curves, effective nonlinear coefficients, spectral and angular phase-matching widths were calculated. B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 177–184, March–April, 1999.     

Infrared filters and analyzers of the composition of substances based on them

Results of investigations on designing band dispersion and dispersion-interference filters for the 4–30 μm IR range and cutoff filters for the 50–300 μm region are presented. Analyzers of the composition of a substance that are designed on the basis of band IR filters and analysis procedures are described. 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. 5, pp. 734–744, September–October, 1998.     

Energy transfer in chemical dimers of porphyrins and chlorins by the methods of selective laser spectroscopy at 1.8–10 K

The methods of selective laser spectroscopy applied at 1.8–10 K to a glass-forming tetrahydrofuran-toluene (3∶1) mixture have revealed that in the dimers of tetrapyrrole compounds (ethane-bis-octaethylporphyrins, ethane-bis-Zn-octaethylchlorins, heterodimers of Zn-cyclopentane porphyrins) the exciton interactions (V₁₂≈118 cm⁻¹) and S-S-transfer of energy (of probability F≈11 sec⁻¹) are implemented under conditions of substantial inhomogeneous broadening (δF_1/2≈50 cm⁻¹). Upon excitation of a donor component in the dimers, one observes a strong quenching of its emission, the disappearance of the fine structure in the fluorescence spectra, a decrease in the efficiency of spectral hole burning by, approximately, an order of magnitude, and a 12-fold increase in their halfwidth. To whom correspondence should be addressed. 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. 500–504, July–August, 1999.     

A method for continuous control of the refractive index of liquids in capillaries

An interference method for controlling the refractive index of liquids pumped through a capillary is considered. The liquid is sounded by two systems of interference bands, the period of which differs by an insignificant value prescribed by the condition of nonius coincidence. An analytical expression is obtained to calculate the refractive index of the liquid controlled in automatic reading of the interference patterns. Institute of Electronics, National Academy of Sciences of Belarus, 22 Logoiskii Trakt, Minsk, 220841, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 6, pp. 832–835, November–December, 1999.     

Dynamics of a waveguide pulsed-periodic CO2 laser with loss modulation

The nonlinear dynamics of a waveguide CO₂ laser with combined periodic loss and pumping modulation is investigated theoretically and experimentally. The possibilities of controlling time and energy parameters of the output radiation using the corresponding selection of the detuning of the cavity's longitudinal mode from the center of the amplification line, the amplitude, and the frequency of loss modulation are demonstrated. The observed asymmetric dependence of the lasing-radiation density on the detuning of the cavity frequency is explained by the attendant modulation of the refractive index of the loss modulator. To whom correspondence should be addressed. 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. 4, pp. 471–478, July–August, 1999.     

Kinetics of the Excited States of Helium in an Atmospheric-Pressure Glow Discharge in a Helium-Nitrogen Mixture

Using an atomic-absorption spectral analysis technique, we determined the concentrations of helium atoms in states 2¹S, 2¹P, 2³S, and 2³P in an atmospheric-pressure glow discharge in helium (99.98%) and in a mixture of helium with nitrogen (99.5%He+0.5%N₂). It is shown that the population of the lower excited levels of helium atoms (n = 2) in its mixture with nitrogen is almost an order of magnitude smaller than in the case of a discharge in helium. The maximum of the concentration of excited atoms in a discharge both in helium and in its mixture with nitrogen is in the cathode region at a distance of about 0.1 mm from the cathode. The reaction of quenching of excited helium atoms by nitrogen molecules is responsible for the sharp decrease in the concentration of He(n = 2) on addition of nitrogen into helium. Presented at the 5th Symposium on Physics and Diagnostics of Laboratory and Astrophysical Plasmas, Belarus, Serbia and Montenegro, Minsk, Belarus, September 20–23, 2004; 12th International Congress on Plasma Physics, October 25–29, 2004, Nice, France. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 4, pp. 530–537, July–August, 2005.     

Amplitude-detuning characteristic of a CO2 laser with simultaneous modulation of two parameters

Analytical expressions have been obtained in a linear approximation for the amplitude-detuning characteristic of a CO₂ laser with simultaneous modulation of two its parameters. It is shown that the value and form of the laser response can be controlled over a wide range by way of changing the modulation frequency, the value of the detuning, and the phase difference of the oscillations of the simultaneously modulated parameters. B. I. Stepanov Institute of Physics of the Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 190–196, March–April, 1997.     

IR spectra and the structure of plasticized cellulose acetate films

This study is carried out to investigate the effect of different plasticizers on characteristics of IR spectra of cellulose acetates. It is found that processes of intermolecular interaction between macromolecules of the polymer and molecules of plasticizing materials result in a shift of absorption bands of acetate groups and in changes in attenuation indices for absorption bands of plasticizers and residual hydroxyl groups in the polymer. The deviation of both the positions of frequencies and attenuation indices is determined by the type and concentration of the plasticizer and by the content of bound acetic acid in cellulose acetate films. 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. 869–876, November–December, 1998.     

Photophysical properties of mesonitrophenyl-substituted porphyrins and their dimers at 295 K

It is shown that at 295 K in meso-orthonitrophenyl-substituted octaethylporphyrins and their chemical dimers the steric interactions of the nitro-group and the volume substituents at β-positions of the pyrrole rings favor direct overlapping of molecular orbitals in a donor-acceptor pair. The efficient quenching of fluorescence of the nitroporphyrins in toluene is attributed to direct nonadiabatic electron transfer from the S₁-level of a porphyrin to the lower-lying state with charge transfer by the “through-space” mechanism. Quenching of the T₁-states is related with heat-stimulated transmission to the higher-lying states with charge transfer of the ion-radical pair as well as with enhancement of the probability of the nonradiative T₁→S₀-transition. To whom correspondence should be addressed. 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. 531–535, July–August, 1999.     

Spectropolarization investigations of the region of the cathode drop in the potential of a helium glow discharge at atmospheric pressure

The dimensions of the region of the cathode drop in potential in a helium glow discharge at atmospheric pressure (in Kiselevskii’s plasma source) are determined. Using Stark spectroscopy of the Balmer-series hydrogen line H_β the spatial distribution of the constant and variable components of the electric-field strength is measured. 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. 3, pp. 362–368, May–June, 1999.     

Spectra of the action of photoinduced NH(ND)-rearrangement of cyanosubstituted isobacteriochlorin

Based on the measured spectra of the action of the process of cis-trans-NH(ND)-isomerization of 5-cyano-2,2,8,8,12,13,17, 18-octamethylisobacteriochlorin (H₂-COMiBCh) and its deuteroderivative (D₂-COMiBCh) in polycrystalline matrices of n-octane and r hexale at 4.2 K, it is established that the character of embedding of COMiBCh in the matrices of n-alkanes has a substantial effect on the barrier of dark rearrangement and the rate of photoinduced NH(ND)-rearrangement, while deuteration of the center of a molecule shifts the dynamic equilibrium toward a trans-form in photoexcitation. To whom correspondence should be addressed. 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. 555–559, July–August, 1999     

Investigation of platinum oxide-titanium films by the method of X-ray photoelectron spectroscopy

Platinum oxide-titanium films that are produced by thermolysis of H₂PtCl₆ in the presence of NO ₃ ⁻ on a titanium surface are investigated by the method of x-ray photoelectron spectroscopy. It is shown that making nitrates a part of the composition leads to an increase in the content of oxidized forms of platinum and the appearance of titanium in the film. Belarusian State Technological University, 13a, Sverdlov St., Minsk, 220630, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 4, pp. 536–538, July–August, 1997.     

Investigation of uranyl nitrate extraction from ketone solutions by dimethyl sulfoxide

Based on an analysis of low-temperature luminescence spectra (T=77 K) of UO₂(NO₃)₂·6H₂O solutions in acetone, the mechanisms of formation of a wide group of uranyl complexes in uranyl extraction from solutions by dimethyl sulfoxide are studied. It is shown that to increase the coefficient of uranyl distribution between the solution and solid phase (in the form of UO₂(NO₃)₂·2DMSO) it is necessary to add sulfoxide in small amounts, of about 0.35–0.5 mole per mole of uranyl. One-time introduction of DMSO in amounts of 1–3 mole per mole of uranyl leads to the formation of a number of uranyl complexes that are well soluble in acetone, and to a corresponding decrease in the distribution coefficient. The role of entropy and enthalpy in improvement of the stability of chelate complexes of uranyl nitrate is evaluated. Belarusian State University, 4, F. Skorina Ave., Minsk, 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 358–362, May–Jene, 1997.