Table of contents

The present state of the problem of quasinuclear systems containing antibaryons (B and 2N2 mesons and 2N baryons) is reviewed. A discussion is presented of the experimental data (the resonances which are strongly coupled with the N channel, with masses of about 2 GeV) and of the central theoretical questions (the energy spectra and properties of the quasinuclear systems, the annihilation widths and shifts of the quasinuclear levels, the pp̄ atom, and radiative transitions from atomic states to quasinuclear states).

This review presents briefly the ideas underlying the electron-nuclear double resonance (ENDOR) method and also discusses methods for the analysis of spectra with the aim of obtaining information on the hyperfine and quadrupole interactions of paramagnetic centers with lattice nuclei and illustrates the potentialities of the ENDOR method in the determination of the structure and properties of impurity centers. Apart from these traditional topics, the attention is concentrated on new aspects of the ENDOR method: influence of external agencies (electric field, pressure, and temperature) on the ENDOR spectra, ENDOR dynamics, optical detection, etc. A demonstration is given of the capabilities of the ENDOR method in investigations of the fundamental characteristics of crystals, such as the energy band structure, local properties near defects, spin-phonon interaction characteristics, excited states of local centers, etc. This demonstration is illustrated by examples of ENDOR studies of electron and hole centers in insulators and semiconductors.

In this review we analyze the current state of experiments and theory relating to the cathode spot of a vacuum arc. We discuss technical features of the experimental study of the near-cathode region of a vacuum arc with high time and space resolution. We discuss in detail the experimental data on such basic parameters characterizing the cathode spot as velocity, nature of motion, and lifetime of the spot, the current to the spot, current density, cathode fall, charge-transfer coefficient, vapor-jet velocity, charged-particle concentration, and electron temperature. We evaluate the reliability of the results obtained by various authors. A classification of cathode spots is proposed, and conditions for the existence of various types of spots and the behavior in the transition from one type to another are described. On the basis of the experimental data considered, we propose the explosive and diffusion models which provide qualitative and sometimes quantitative descriptions of cathode spots of various types.