Deformation-induced nonradiative decay of color centers in alkali halides

Abstract

It is shown that the coloration of the microcrystalline powders of KCl, KBr, and KI is completely lost within 24 h when the colored powders are stored in dark, at room temperature, whereas the single crystals of these materials subjected to the same treatment can retain the coloration for at least several years. The decay of color centers is through nonradiative modes. The presence of alkali and halogen impurities greatly influences the decay in the powders. It is suggested that the decay involves dislocation motion and such experiments can give important information about defect interactions.