Table of contents

CONTENTS 1. Introduction 671 2. High-resolution Rotational and Rotational-vibrational Spectra 672 3. High-temperature Spectroscopy of Vapors. Structure Applications 675 4. Matrix Isolation Method 676 5. Resonance Effects 677 6. Applications Outside the Laboratory: Lidar Studies of the Atmosphere, Plasma Diagnostics, and Other Possible Applications of Remote Spectroscopy 682 Literature Cited 685

CONTENTS I. Introduction 688 H. Shock-wave modes 689 III. Equilibrium thermal-conduction modes 691 IV. Nonequilibrium and other modes 701 References 706

The fundamental results of recent research on the propagation of elastic microwaves (hypersonic waves) in crystals of various types are considered. The procedure for experiments with hypersonic waves is briefly described. The characteristics of the propagation of elastic waves in crystals (polarization, velocity, energy flux) and methods of their calculation are given. The principal mechanism of damping of hypersonic waves are considered, such as interactions with thermal phonons by the Akhiezer mechanism and by the Landau-Rumer mechanism, and interactions with free carriers and with defects. A separate chapter is devoted to problems of the propagation of hypersonic waves in magnetically-ordered crystals and their interactions with spin waves. The scattering of light by hypersonic waves is also considered, the singularities of this phenomenon are discussed, as is its use for the investigation of the characteristics of elastic-wave propagations. Some conclusions are drawn from the point of view of the prospects of using hypersonic methods in solid-state physics research.

TABLE OF CONTENTS 1. Introduction 728 2. Crystal Structure 728 3. Optical Properties and Band Structure 732 4. Electrical and Galvanomagnetic Properties 734 5. Antifriction Properties 738 6. Conclusions 739 Bibliography 740

The review covers theoretical and experimental studies of the parametric effect of high-power electromagnetic radiation on a plasma. Under the action of such a field, parametric instabilities develop in a plasma, leading to appearance of a turbulent state with an increased level of fluctuations of the internal field in the plasma. Under the action of these fluctuations the particle distribution in the plasma changes and, in particular, their energy increases, which corresponds to anomalously fast transfer of the energy of the radiation field to the plasma particles or, in other words, corresponds to an anomalous increase of the high-frequency conductivity of a parametric ally unstable plasma. This theoretically predicted pattern find confirmation in a number of experimental investigations, also discussed in the review. Experiments demonstrate the appearance, under the action of high-power radiation, of an increased level of plasma fluctuations, a large high-frequency resistance, an increase in the rate of plasma heating, and, finally, of fast particles. All of these effects are consistent with the theoretical ideas and permit us to discuss qualitatively a new group of physical phenomena arising in the action of high-power radiation on a plasma.

This article reviews the current status of the theory of vibrational relaxation in gases and its applications to the theory of molecular lasers. We discuss relaxation of the vibrational energy of diatomic and polyatomic molecules as represented by harmonic-oscillator models. The vibrational kinetics in a system of anharmonic oscillators is analyzed in detail. We treat quasi-steady-state population distributions of vibrational levels that arise under substantially non-equilibrium conditions, both in a singlecomponent molecular system and in gas mixtures. We discuss relaxation that proceeds in the presence of sources of vibrationally-excited molecules: infrared resonance radiation, recombination, and dissociation; in particular, we analyze the process of non-equilibrium dissociation at low gas temperatures. We discuss from a unified standpoint based on vibrational kinetics the working mechanisms of lasers using vibrational-rotational transitions in diatomic and polyatomic molecules with various means of excitation (electrical, chemical, and gas-dynamic).

CONTENT 1. Introduction 786 2. Binary Stars 788 3. Orbit Variations of the Close Pair 790 4. Evolution of Stars in Close Binary Systems 792 5. Successes and Failures of Theory 795 6. Novae and Binary Stars 796 7. "Black Holes" 797 8. Use of Close Binaries to Test Theories of the Internal Structure of Stars 799 Cited Literature 801

The review considers the recording and reproduction of complete as well as partial information concerning the vector characteristics of a field. The principal methods and features of producing a complete recording of the wave polarization are indicated, namely the use of two reference beams with orthogonal polarizations, coding the reference beam with random wave fronts, and the use of three-dimensional holograms. Different aspects of the use of holographic recording of partial information concerning field polarization are considered. In such a procedure, the information on the polarization characteristics of the object wave is coded by means of other field characteristics, the amplitude and the phase. In this connection, in analogy with the phase-contrast method, the concept of polarization contrast is introduced and defined as the transformation of the changes of the state of polarization over the object into variation of the intensity of the image reconstructed from the hologram. The production of holograms by this procedure is described consistently with the aid of the correlation-matrix formalism, and also with Stokes parameters. The intensity of the virtual image is expressed in terms of the coherence matrix of the object and reference waves, or else with the aid of corresponding Stokes parameters. It is shown that the polarization state of the reference wave serves as the analyzer of the vector characteristics of the object field. The method of double exposure using orthogonally linearly polarized waves for different exposures is compared with the method of single exposure with circularly polarized fields. Certain limitations imposed on the objects and conditions of the experiment, under which both methods coincide, are indicated. Experiments with a very simple object, illustrating the procedure, are described.