Table of contents

Research on the electron-hole liquid in a semiconductor is reviewed. The basic properties of the liquid, their theoretical description, and methods for studying them experimentally are discussed. The behavior of an electron-hole liquid in external electromagnetic and stress fields, the motion of droplets of the liquid, and the interaction of the liquid with nonequilibrium phonons (the phonon wind) are described.

This review presents the results of experimental and theoretical studies to detect and investigate deep levels associated with impurities and intrinsic defects in A^IV B^VI semiconductors. Group-III impurities are discussed in greatest detail. The experiments (electrophysical, optical, thermophysical) indicate the existence of localized and resonance states in materials doped with indium and thallium, and also (less unambiguously) with gallium and aluminum. Stabilization of the chemical potential is especially clearly manifested in indium doping, and it leads to an extremely high electrical homogeneity of the specimens, as revealed by the long-term relaxation of the concentration of nonequilibrium electrons. The Fermi level substantially varies with the composition of the material, the temperature, and the pressure. Upon doping with thallium, one observes a strong resonance scattering of holes, an electronic heat capacity arising from the impurity, and superconductivity caused by the presence of resonance states. The theoretical and experimental data on localized and resonance states associated with vacancies and complexes of intrinsic defects, and also with impurities of transition metals, bismuth, cadmium, tin, and germanium are reviewed. The genesis of the levels, the energy of interaction of electrons at an impurity center, relaxation mechanisms, and superconductivity are discussed.

A review is given of accelerators and colliding-beam installations operating at center-of-mass energies between 7 GeV and about 50 TeV. The basic principles underlying the design of such systems and ways of increasing the energy and intensity of accelerated-particle beams are briefly discussed. The scale of modern machines is illustrated by considering the examples of the proton synchrotron at the Institute of High Energy Physics at Serpukhov, the accelerating and storage complex at CERN, the accelerators at the Fermi National Accelerator Laboratory in the USA, the electron-positron storage complex in Hamburg, and the Stanford Linear Accelerator in the USA.

A new direction in the field of x-ray optics is discussed. This new direction is associated with diffraction at grazing angles of incidence and diffraction; it is associated with the excitation of x-ray surface waves and quasiwaveguide modes, and with the study of the angular and energy dependences of the reflection spectra. An analysis of theoretical and experimental investigations in this area is carried out with the aim of determining the possibility of using these diffraction and reflection features for the study of surface layers, thin films and interfaces. The extremely asymmetric two- and multiwave diffraction schemes and the two-wave symmetric noncoplanar diffraction scheme are analyzed, as is the anomalous reflection of the x-rays. The angular dependences of the anomalous reflection are calculated on the basis of a model of a nonuniform surface layer. It is shown to be possible to use the angular dependence of the reflection for the determination of the statistical characteristics of surface nonuniformities. Experiments for the determination of short range order in surface films on the basis of the analysis of the extended fine structure of reflection spectra are discussed.