Thermally stimulated processes related to photochromism of scandium doped sillenites

Abstract

The low temperature photochromism of the scandium doped sillenites was investigated. The time dependence of the light induced absorption was measured for different conditions of the stimulation process. The optical coloring spectrum and the optical bleaching spectrum have been established on the basis of the obtained kinetics. The distinction between short time illumination (<20 s) and long time illumination (>1000 s) in the coloring process has been noticed. The thermal bleaching curves obtained for the different conditions of illumination provided information about energy of the shallow trap levels responsible for the thermal stability of the photochromic effect. It has been shown that there are five energy levels involved in the thermal bleaching processes but their activity is strongly related to the conditions of illumination. Some arguments are presented that the investigation of thermal bleaching could be used as a good tool for the shallow trap spectroscopy as it is in the conventional thermoluminescence and measurements of thermally stimulated currents.