Sonoluminescence in X-Rayed KCl Crystals

Abstract

Luminescence induced by 100 kHz ultrasonic excitation in X-rayed KCl crystals which previously are heated in chlorine vapor is observed at room temperature. Under prolonged excitation by a constant ultrasonic stress amplitude, the luminescence continues during initial several tens seconds. Simultaneous measurements of internal friction are carried out by the Marx’s method in order to reveal a role of dislocation motion in the luminescent processes. Existence of critical strain amplitudes was found above which the luminescence becomes notable and the internal friction indicates an abrupt increase. The results are discussed with the vibrating string model of dislocation motion, and it is concluded that excitation of color center’s electrons is caused by unpinning of dislocation and that the unpinning process annihilates defects that have pinned the dislocation.