Elektronenspinresonanz- und optische Untersuchungen zur FarbzentrenreaktionF⇄F′ in KCl-Kristallen

Abstract

Simultaneous measurements of optical absorption and electron spin resonance of additively colored KCl crystals have been carried out during the optical bleaching ofF-centers at −90°C. TheF-center resonance signal does not change in its significant properties e.g. line shape, line width,g-value, and saturation behavior, but it decreases proportional to the decrease of the opticalF-center absorption band. No ESR-signal due to theF′-center could be observed. The time dependence of theF⇄F′-center conversion has been investigated by ESR and optical measurements. It does not give any indication of a paramagnetism of theF′-center, too. The kinetics of the thermal decay of theF′-center at −90°C have been studied. One can interpret the time dependence of this process, if one assumes that the mean lifetime of anF′-center depends on the distance of the nearest halogen ion vacancy. The expectation of life of theF′-centers therefore increases during the thermal decay, as the mean distance between remainingF′-centers and vacancies increases.