Table of contents

Theoretical studies on the effect of generation-recombination aggregation of Frenkel defects created by irradiating solids with radiation are reviewed. We discuss the way in which a substantially non-Poisson spectrum of density fluctuations of the number of defects is formed by the stochastic creation and recombination of immobile and mobile defects. The results obtained by using different approaches are compared—multiparticle densities, diagram technique, scaling, computer simulation. We show that the aggregates created in the course of accumulation of sametype defects (atoms or vacancies) substantially affect the kinetics of defect accumulation and increase severalfold their concentration at saturation at large radiation doses. We examine in detail how the spatial distribution of defects depends on their mobility, on the dimensionality of the space, on correlation in genetic pairs being created, on the mechanism of recombination (annihilation or tunneling charge-transfer), and on the number of crystal-lattice nodes in the sphere of recombination. Experimental data confirming the calculations are presented.

The basic physical principles of resonance hyper-Raman scattering (RHRS) of light by media in different aggregate states are examined. The theory of RHRS by molecules, which takes into account the vibronic interaction between the resonance electronic states of a molecule, is presented. Expressions are given for the components of the tensor of RHRS in vibrational and vibrational-rotational transitions. The selection rules, the symmetry of the RHRS tensor, the polarization characteristics of the process, and the ratios of the intensities of scattering by totally and nontotally symmetric vibrations and their overtones are discussed. The results of experimental investigations of RHRS by molecules in the gas phase and molecules adsorbed on ultradispersed particles of silver are presented. These results confirm that the proposed theory adequately describes the actual process of RHRS qualitatively and in a number of cases quantitatively also, and they demonstrate that RHRS is a good source of spectral information. Data on RHRS by phonons in solids, for which there is still no theory, also show that RHRS spectroscopy could potentially yield a great deal of information.

Originally, he says, man was round, his back and sides forming a circle. Hermann Weyl, "Symmetry" (on Plato's Dialogue "Symposium"). The evolution of polarization (alignment and orientation) of angular momenta of diatomic molecules both in the ground and excited states upon absorption of light is examined. The effect of external factors—magnetic field and collisions—on this polarization is investigated. Interference effects (level crossing, quantum beats, beat resonance) and the possibilities of employing them to determine magnetic and relaxation characteristics of individual vibration-rotation levels are analyzed. A classical description of phenomena is given in terms of distribution of angular momenta, including the use of isometric projections of the distribution being formed. Equations are given that describe the interaction of intense laser radiation with an ensemble of molecules in the gas phase. Other mechanisms are presented for the evolution of angular momenta for the ground electron state of diatomic molecules.