Table of contents

We review the literature on electron-vibrational interactions in polyatomic molecules. The analysis is based on an adiabatic theory that employs a single universal small parameter of the molecules, viz., the Born-Oppenheimer parameter. The principal results of the theory of electron-vibrational spectra are summarized. Special attention is paid to to the results that follow from a general analysis that is not based on concrete model. The theory is compared with experimental data for a wide range of chemical compounds (hydrocarbons with various structures, heterocyclic compounds, dyes). Possible mechanisms of broadening the electronvibrational line in liquid and solid solutions are discussed. Experimental data that demonstrate the role of various broadening mechanisms in concrete cases are cited. It is demonstrated by means of a number of examples (induced optical activity, dimers, excimers) that the adiabatic theory is significant in the analysis of the influence of intermolecular interactions on the spectral characteristics of the molecules. The theoretical analysis is illustrated with experimental data. The role of the adiabatic theory in the description of nonradiative transitions in polyatomic molecules is briefly considered. Particular attention is paid to a discussion of the role of chemical processes that accompany nonradiative transitions. Some additional problems faced by theory and experiment are indicated in the conclusion.

This review is concerned with the propagation of electromagnetic waves in magnetically ordered crystals, including the subjects of circular, linear, and elliptic birefringence. New optical phenomena in crystals are analyzed on the basis of magnetic symmetry. Microscopic mechanisms of magneto-optic effects suggested so far are reviewed. Problems in crystal optics of magnetically ordered media are considered. The main results of experimental investigations of magnetic birefringence of light in ferromagnets, ferrimagnets, and antiferromagnets are discussed.

This paper contains an exposition of the classical hydrodynamical interpretation of multiple hadron production processes. Special attention is given to the clarification of the fundamental aspects of the hydrodynamical theory, the analysis of nucleon-nucleus collisions, and e⁺e^– annihilation into hadrons. The conclusions of the theory are compared with experimental results. Some heuristic aspects of the theory are outlined. Use is made of the literature up to the beginning of 1975.

An analysis is made of the use of high-voltage electron microscopes in solid-state physics research. The most promising fields of application of high-voltage electron microscopes are discussed; these involve mainly research on the mechanism of the action of radiation on solids.

Several nontrivial questions are discussed which arise in obtaining and utilizing boundary conditions along moving surfaces separating two media and which are associated with characteristics features of electrodynamic material equations. It is noted that the boundary conditions themselves can depend on the relationship between the thickness of the boundary and the proper times of the motion of the particles of the medium (and even simply on the velocity of the boundary). In view of the inertial properties of the medium all the electrodynamic quantities remain continuous (the law of continuity) at an ideally sharp discontinuity of its parameters in time. An exception is presented by the case of the motion of the boundary with velocity c, and also by discontinuities "frozen into" the medium. For a more smoothly varying (although sharply varying compared to the external scale of variation of the field) boundary layer one can neglect the inertial properties (dispersion) of the medium; in this case the field and the polarization undergo a "discontinuity." However, in this case difficulties of another kind arise when the velocity of the boundary is "above light velocity" on one side and "below light velocity" on the other side (in particular, the interaction of small perturbations with shock waves belongs to such a case); these cases require a separate investigation. The effect of the inertial properties of the medium on the boundary conditions is illustrated on the example of electromagnetic waves in a dielectric with elastic oscillators.

Three independent electrification effects have been found and studied in crystals of lithium fluoride. Upon cleavage, the parts of the crystal become charged with charges equal in magnitude and opposite in sign. As a result of plastic deformation, the crystal becomes a sort of pyroelectric, and an intrinsic electric field appears in it. When the deformed crystal contacts a conductor, the crystal becomes charged with a sign opposite to that of the intrinsic field at the point of contact. An interpretation of the cited effects is given.