Light-induced evaporation and condensation growth of aerosol particles

We analyze the possibility of resonant optical radiation inducing evaporation and condensation growth of aerosol particles suspended in a vapor-gas mixture. The molecules of the vapor absorb radiation selectively as to velocity. We examine the Knudsen regime, in which the particle radius is much smaller than the mean free path of the molecules. Zh. éksp. Teor. Fiz. 113, 1036–1047 (March 1998)     

Thickness dependence of exciton absorption in pure GaAs crystals at the “prequantum” limit

The optical absorption of GaAs crystals with thicknesses d=0.4−4.4 μm is measured in the exciton-polariton resonance region at a temperature of 1.7 K. As the thickness is reduced, both a broadening of the exciton line and increased absorption with a negligible Stark shift are observed. The way the absorption spectra vary with crystal thickness is examined in terms of a competition between two regions for light-exciton interactions in the crystal: in the field of surface charges and electric-field free. Fiz. Tverd. Tela (St. Petersburg) 40, 869–871 (May 1998)     

Study of the phase composition of AgI microcrystals by exciton spectroscopy and differential scanning calorimetry

Differential absorption spectra of RbAg₄I₅ have been measured in the exciton absorption region of AgI within the temperature range 27–250 °C. In the same temperature range, the temperature behavior of the heat capacity of RbAg₄I₅, Rb₂AgI₃, and KAg₄I₅ have been obtained by differential scanning calorimetry. An analysis of the results suggests that, in AgI microcrystals less than r _cr in size, the upper boundary for stability of the low-temperature β modification is higher by several tens of degrees. Fiz. Tverd. Tela (St. Petersburg) 40, 852–854 (May 1998)     

Nuclear pumping of a carbon monoxide laser

It is shown that plasma-chemical processes involving ionized and excited particles can make the main contribution to the pumping of energy into vibrations of carbon monoxide molecules. It is noted that the use of helium as a buffer gas in the active laser medium is not optimal. The employment of argon instead of helium permits a 1.5-fold increase in the efficiency of the pumping of energy into carbon monoxide molecules and an order-of-magnitude decrease in the threshold energy for pumping the active medium. Zh. Tekh. Fiz. 68, 80–85 (July 1998)     

Choosing an adequate mathematical model in problems with high pulsed energy deposition

The problems of choosing the optimal mathematical model for a prescribed range of parameters of a pulsed action are discussed. A preliminary analysis performed by similarity and dimensional-analysis methods using interpolation equations of state of the matter shows that the complete system of equations of gasdynamics can be simplified by dropping individual terms which are not important in a given parameter range. The results of an analysis are presented in the form of nomograms, which also make it possible to identify the class of fast and energy-intensive gasdynamic processes more accurately than at an intuitive level. Zh. Tekh. Fiz. 68, 44–47 (May 1998)     

Effect of thermal broadening on the paramagnetic susceptibility of the Invar alloys Fe65Ni35 and Fe72Pt28

Experimental data is used to show that bulk thermal broadening makes a considerable contribution to the Curie constants of the Invar alloys Fe₆₅Ni₃₅ and Fe₇₂Pt₂₈. Fiz. Tverd. Tela (St. Petersburg) 40, 274–275 (February 1998)     

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)     

Magnetic phases of FexV1−x S and their electronic structure

A study has been made of the Fe_xV_1−x S solid solutions with 0<x<0.5. For the compounds with x>0.1, x-ray diffraction analysis discloses a V₅S₈ superstructure. Samples with x>0.1 are magnetically ordered at room temperature. The concentration dependences of resistivity and magnetization exhibit sharp peaks for x=0.1 and x=0.2, respectively. The main features of the structure and electronic properties have been qualitatively explained in terms of the three-band exciton-insulator model, and the maxima in resistivity and magnetization are assigned to the formation of localized magnetic moments with S=1, which become delocalized with increasing x. Fiz. Tverd. Tela (St. Petersburg) 40, 1890–1893 (October 1998)     

The effect of fluctuations of a classical exterior medium on tunneling nonradiative processes in molecules

We examine nonradiative transitions in molecules with allowance for the effect of a classical polar exterior medium on tunneling charge transport. The approach allows for the vibrational frequencies of a molecule in the electron transition. In the case of slow fluctuations, the theory predicts a low-temperature (non-Arrhenius) increase in the tunneling nonradiative transition rate, and the results agree qualitatively with the experimental data. When the fluctuations of the exterior medium are rapid, at certain values of the molecular parameters the tunneling decay rate is found to decrease with increasing temperature because the conditions needed for resonant tunneling are violated. Zh. éksp. Teor. Fiz. 114, 1944–1953 (December 1998)