Table of contents

The interaction of quantum defects (defectons) with the conduction electrons is considered. A systematic allowance is made for infrared renormalisations which are due to this interaction and which influence significantly the width of the energy band of defectons and their contribution to physical properties of a metal. An analysis is made of the interaction of deflections with one another and with other defects of the crystal lattice of a metal. The processes of quantum defect clusterisation due to this interaction are studied. The temperature dependences of the transport coefficients are derived both for a metal containing both free defectons and two-level systems, which appear in a number of cases when a quantum defect is captured by a heavy immobile impurity.

An analysis of experimental and theoretical investigations is the basis of this state-of-art review of models of fast ionisation waves (FIWs) and of characteristics and properties of these waves. The attention is concentrated on waves with the maximum possible velocities of 10⁹–2×10¹⁰ cm s^–1 when the amplitudes of voltage pulses are 20–300 kV. At low and moderate pressures the reduced intensity of the electric field in the front of a wave is so high that the front becomes a moving source of a beam of high-energy electrons in which the current can reach several kiloamperes. At moderate pressures the high-energy electrons in the wave front overtake the front and cause preliminary ionisation of the gas ahead of the front. At low pressures these electrons determine mainly the mechanism of the motion of the front. At high pressures (in excess of 200 torr) the main source of such preionisation is the radiation emitted by the front. The high rate of filling of the discharge volume with a plasma, high electric fields and high energies of the electrons in the front, and the slight heating of the gas make fast ionisation waves attractive for applications.

Wide bandgap semiconductors are electronic materials in which the energy of the band-to-band electronic transitions exceeds approximately 2 eV. These materials have different kinds of chemical bonds and of crystal lattice structures, but the electronic and optical processes taking place in them have a great deal in common. Diamond, silicon carbide SiC, gallium phosphide GaP, cadmium sulfide CdS, and some other related compounds of the A^IIB^VI type occupy a special place among the widegap semiconductors. Recent developments in optoelectronics and other fields of practical applications (in particular, high-temperature devices and methods of detecting photons and charged particles) have stimulated a wide interest in wide bandgap semiconductors. The data available for some of the most widely studied members of the very large family of wide bandgap semiconductors have been used to analyse the most characteristic properties of the processes taking place in these materials, and especially those induced by the strong excitation of their electronic subsystem and by the phenomena associated with the unavoidably present carrier localisation centres.

The computer ab initio simulation and analytical theory that revealed unexpected nonergodic properties in a classical Coulomb plasma are reviewed. The results of a many-charged-particle system simulation predict the possible existence of a real metastable plasma, supercooled with respect to its degree of ionisation. The existence of such a plasma state is a consequence of the entropy conservation in isolated Hamiltonian systems free from any stochastic action from outside. The occurrence of a metastable supercooled plasma similar to a supercooled vapour or superheated liquid depends on two conditions. Firstly, all the charged particles should behave exactly according to the laws of classical mechanics (hence, most negatively-charged particles should preferably be heavy ions). Secondly, the plasma ionisation degree should be sufficiently high (α > 10⁻³) . It is shown from thermodynamic considerations that a mixture of a supercooled plasma with an ideal gas might form a plasmoid of the ball lightning type.

The history and physical prerequisites for the realization of the Sagnac experiment, that is of the 'vortex optical effect' in the frame of a rotating interferometer, are considered. General relativity is used to develop the theory of propagation for electromagnetic waves in a noninertially moving material medium. The theoretical analysis of the peculiarities of the X-ray and gamma-radiation diffractions has been performed within the system of the three-mirror monoblock crystalline interferometer and resonator, while taking into account their rotations. Experimental studies of the X-ray 'vortex optical effect' were performed on a specially designed autonomous X-ray apparatus (commonly used for X-ray interference investigations), which was put on the rotating platform. A series of fluctuation effects (the temperature drift, the field of random deformations, etc.), which keep the Sagnac experiment out of reach of the limiting accuracy, have been revealed and investigated. The experimental data, obtained in the investigation of the 'vortex optical effect', are compared with the results of the theoretical analysis.

A new approach to the study of antiferromagnetic phenomena in terms of the exchange magnetic structure code is examined. If the positions of the magnetic ions are known this code could play the same role in the symmetric description as the international symbol for the crystallographic space group plays in the description of the properties of nonmagnetic crystals.