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The effect of subnanosecond laser pulses on the structure and electronic subsystem of extended defects in cubic semiconductors was studied using cadmium telluride (CdTe) as an example. A CdTe epitaxial film containing threading dislocations was exposed to pulsed laser emission at helium temperatures. This exposure led to a local rearrangement of dislocation, while the properties of the crystal lattice remained undisturbed. The rearrangement was visualized in situ via an observation of the single luminescent centers associated with the partial dislocation cores. The rearrangements in the center of the laser spot, as well as those far from this location, were detected, thus revealing the laser treatment's non-thermal, relatively long-range influence. We associated the corresponding mechanism with Peierls's gliding of dislocation under the impact of laser-induced hypersonic surface waves. The results we obtained are of interest in the development of all-optical methods for the local laser processing of extended defects in CdTe and subsequent expansion those methods to other A 2 B 6 cubic semiconductors. [ABSTRACT FROM AUTHOR]

We report the results of comparative studies of ion-pair formation and quenching processes in collisions of Rydberg Li(nl) and Cs(nl) atoms with Ca(4s2), Sr(5s2) and Ba(6s2) atoms possessing small electron affinities. Our consideration includes both the cases of selectively excited Rydberg nl-states with small orbital angular momentum (l ≪ n) and nearly circular states with l ∼ n − 1. Calculations of the electron-transfer processes are based on the semiclassical theory of nonadiabatic transitions and exact expression for the Rydberg-covalent–ionic coupling terms. Calculations of nonresonant quenching processes are carried out within the framework of the available theory of inelastic and quasielastic transitions between Rydberg-covalent states. The ion-pair formation and resonant quenching cross sections are shown to be significantly dependent not only on the principal quantum number n but also on the orbital angular momentum l and the binding energy of the alkaline-earth anion. For each system under study we find the regions of n in which either the resonant quenching or the ion-pair formation processes are predominant. The relative role of the resonant and nonresonant mechanisms of depopulation of Rydberg states is investigated. [ABSTRACT FROM AUTHOR]

Electron-transfer processes are studied in thermal collisions of Rydberg atoms with alkaline-earth Ca(4 s2), Sr(5 s2), and Ba(6 s2) atoms capable of forming negative ions with a weakly bound outermost p-electron. We consider the ion-pair formation and resonant quenching of highly excited atomic states caused by transitions between Rydberg covalent and ionic terms of a quasi-molecule produced in collisions of particles. The contributions of these reaction channels to the total depopulation cross section of Rydberg states of Rb( nl) and Ne( nl) atoms as functions of the principal quantum number n are compared for selectively excited nl-levels with l ≪ n and for states with large orbital quantum numbers l = n − 1, n − 2. It is shown that the contribution from resonant quenching dominates at small values of n, and the ion-pair formation process begins to dominate with increasing n. The values and positions of the maxima of cross sections for both processes strongly depend on the electron affinity of an alkaline-earth atom and on the orbital angular momentum l of a highly excited atom. It is shown that in the case of Rydberg atoms in states with large l ∼ n − 1, the rate constants of ion-pair formation and collisional quenching are considerably lower than those for nl-levels with l ≪ n. [ABSTRACT FROM AUTHOR]