Stability of solutions to the Cauchy problem for a plane hyperbolic system with time-periodic coefficients

Considering a plane hyperbolic system with time-periodic coefficients, we construct a version of the direct Lyapunov method with the condition on the derivative of the Lyapunov functional along the trajectories of the system which is weakened by use of periodicity of the coefficients. We exhibit an illustrative example.     

Excitons in ZnP2 crystals in the electric field of a Schottky barrier

A study is made of the effect of electric fields on the exciton states of β-ZnP₂ crystals (T=77 K) in structures with Schottky barriers formed by depositing semitransparent electrically-conducting InSnO₂ films on the crystal surface. The observed changes in the exciton optical reflection spectra when an electrical potential is applied to a barrier are explained by the shift and broadening of the exciton level caused by the Stark effect. The experimental data are compared with calculations based on a theory of exciton optical reflection from planar spatially nonuniform structures. Fiz. Tverd. Tela (St. Petersburg) 40, 884–886 (May 1998)     

Spectroscopic factors of9Be,10B and13C from (d,t) reactions

The differential cross sections of tritons from the (d, t) reaction on⁹Be,¹⁰B and¹³C targets have been measured in the angular range of 5° _LAB110° with relatively small errors, 5%. The experimental data were analysed in terms of the standard DWBA using both zero-range and exact finite-range approaches.     

A method to calculate density distribution of adsorption centers from temperature-programmed desorption spectra

A new method to calculate the function of density distribution of adsorption centers according to the activation energies of desorption by using temperature-programmed desorption curves is suggested. The application of this method is exemplified by toluene desorption from ZSM-5 zeolite.

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Luminescence analysis of complex organic materials based on resolved line spectra produced by selective laser excitation

Selective methods of obtaining the resolved line spectra of the solutions of complex molecules, along with the peculiarities of these spectra, are considered. At sufficiently low temperatures (4.2 K), broad-band absorption and luminescence spectra of the solutions of organic compounds are often broadened, mainly inhomogeneously. Excitation of the luminescence by tunable lasers can eliminate this broadening. The spectra obtained consist of dozens of narrow (Δv ≈ 1 cm^-1) vibrational lines. Some examples of selective excitation for the spectrofluorimetric analysis of complex organic materials are given: identification (at the 10^-11 g ml^-1 level) and determination of individual polynuclear hydrocarbons in certain materials without preliminary separation is demonstrated by the determination of benzopyrene and perylene in gasoline and the detection of perylene in a solid paraffin.     

Application of frequency converters to femtosecond laser radiation for lidar monitoring of the atmosphere

Possibilities of using superbroadband nonlinear-optical frequency converters for femtosecond laser pulses in lidar sensing of the atmosphere are analyzed. New biaxial nonlinear crystals in which the conditions of phase and group matching can be satisfied simultaneously are basic elements of frequency converters. A technique for the broadband lidar sensing of the gas composition of the atmosphere based on the differential optical atmospheric spectroscopy and the differential absorption methods is described. The lidar sensing of gas constituents of the atmosphere using frequency converted femtosecond laser radiation is simulated numerically.