The ESR method was applied to a Y 3 Al 5 O 12 crystal at 300 K to establish a photostimulated charge transfer in iron and chromium impurity ion systems at 450-320 nm: Fe 2+ → Fe 3+ , Cr 3+ → Cr 2+ . Near 150 K, the thermally stimulated and photostimulated change in the valence state of chromium, iron, and intrinsic defects, and the recombination processes are governed by electron traps with activation energy ∼0.14 eV. Apart from the initial stage, the charge recombination is satistactorily represented by the Forster equation

The ESR method was applied to a Y 3 Al 5 O 12 crystal at 300 K to establish a photostimulated charge transfer in iron and chromium impurity ion systems at 450-320 nm: Fe 2+ → Fe 3+ , Cr 3+ → Cr 2+ . Near 150 K, the thermally stimulated and photostimulated change in the valence state of chromium, iron, and intrinsic defects, and the recombination processes are governed by electron traps with activation energy ∼0.14 eV. Apart from the initial stage, the charge recombination is satistactorily represented by the Forster equation

The authors study the excitation of stimulated emission of Ho/sup 3 +/ ions in a single crystal of YAlO/sub 3/ by waves of inter-Stark transitions of three generation channels /sup 5/S/sub 2/ to /sup 5/I/sub 5-7/ at 300 K with optical pumping. They also measure the main luminescence characteristics.

A study was made of the influence of unstable defects on the generation of laser radiation in YAG:Nd3+ crystals. It was found that F+ centers and iron impurity ions were the main unstable defects. The influence of these defects on lasing was manifested in different temperature ranges. At temperatures 287-312 K the F+ centers predominated, whereas above 312 K the effect was mainly due to iron impurity ions.

An investigation was made of optical breakdown at defects and in defect-free regions of lithium iodate crystals in the case of single and repeated action of laser radiation. The likely mechanism of optical breakdown involving participation of paramagnetic impurity ions was considered.

The Hutson-White theory is extended to the case when there are mobile charge carriers of both signs in a piezeosemiconductor. Expressions are obtained for the damping and velocity of the longitudinal sound wave being propagated along the z axis in the piezosemiconductor as a function of the magnitude of the longitudinal electrical field, as well as for the constant current density originating here. It is shown that the acoustic wave changes the conductivity of a piezosemiconductor with mixed conductivity. A method is proposed for determining the mobility simultaneously of both the positive and negative carriers in an intrinsic piezosemiconductor.