Table of contents

A review is made of the current status of research on the nonlinear photoelectric emission resulting from the action of high-power laser radiation. The main experimental results are considered and possible theoretical interpretations are discussed. Considerable attention is concentrated on topics investigated recently, such as photoelectric emission in electrolyte solutions; photoelectric emission under the action of ultrashort laser pulses; detailed time, polarization, energy, and some other characteristics of photoelectric emission. Methods and results of calculations of the nonlinear photocurrent from the surfaces of metals are described. Theoretical results obtained by various methods are compared with one another and with the experimental data.

This article reviews the fundamental experimental and theoretical results on the nature of radiation defects and the mechanism of their production in ionic (mainly alkali-halide) crystals. We show that one can produce high concentrations of radiation defects in these crystals by irradiating with photons and particles whose energies do not suffice to displace atoms from lattice sites in elastic collisions with them. On the other hand, excitons and band holes in these crystals have a tendency to autolocalize in the regular lattice. In certain electronic states, excitons prove to be unstable with respect to decay into Frenkel' defects. This is the reason for the low radiation stability of many ionic crystals. We discuss the mechanisms of the above-cited instability and of secondary processes (localization, recombination, charge transfer) in which the products of exciton decay participate, as well as a possible role of such processes in other types of solids.

The synthesis conditions, certain problems of epitaxial growth, and methods of controlling the quality of single-crystal iron-garnet films are discussed. The main physical properties of garnet films are considered, such as optical absorption, Faraday rotation, the characteristic length, the saturation magnetization, the coercive force, the magnetic anisotropy, the mobility, and the dynamic transformation of domain walls. Measurement methods and some results of the investigation of these properties are described. The reproducibility and the temperature dependence of the principal parameters of the films are discussed.

The Minkowski tensor gives g^M = nu/c (I) for the momentum density g of a plane-wave electromagnetic field in a stationary medium, whereas the Abraham tensor gives g^A = u/nc (II), where u is the energy density and n the refractive index. Expression (I) cannot be reconciled with J = μν (III), where μ is the mass of the wave packet and ν is its velocity if, according to Einstein, μ = E/c², where J is the momentum and E the energy of the wave packet. On the other hand, the expression for the "pseudomomentum" J^M = nE/c (IV), which follows from (I), is identical with the expression for the momentum of the quantum photon J = nhν/c (V), whereas the formula the follows from (II), i.e., J^A = E/nc (VI) is in agreement with the Einstein equation (III) but is in conflict with (V). Simple calculation for stationary medium and source shows that (IV) and (VI) can be reconciled if one takes into account the fact that, under certain assumptions, J^M = J^A + ΔJ (VII), where ΔJ is the momentum communicated to the medium in the photon emission process. It is shown in this paper that, within the framework of the adopted assumptions and, probably, classical models generally, expression (VII) cannot be generalized to the case of a source moving relative to the medium. This result is in conflict with the conclusions reported by V. L. Ginzberg and V. A. Ugarov [Usp. Fiz. Nauk 118, 175 (1976)] [Sov. Phys. Usp. 19, 94 (1976)]. Moreover, it is shown that, if (VII) is introduced as a postulate for a source moving relative to the medium, one can satisfy at the same time both the quantum conditions and (V), on the one hand, and the fundamental Einstein relation (III), on the other.

During the present century due to an increase in the number of people on the earth's globe and with a growth of material culture technological and energetic processes have begun to take place which have started to alter the nature of the whole globe. Some of these changes have become so significant as to constitute a danger for the safe existence of humanity as a whole. In this paper it is shown that global problems usually develop according to exponential laws when an acceleration of the processes acquires the character of an explosion. The solution of global problems consists of bringing them under control and preventing an explosion. One of the problems is associated with the depletion of energy resources which are a basic factor determining the level of contemporary civilization. It is shown that the only way to escape the crisis consists of making a transition to atomic energy. An examination is made of the technical, scientific and social diffuclties which lie in the path to this solution and which it is necessary to resolve.