Color Centers in Additively Colored CsBr

Abstract

Color centers have been studied in CsBr single crystals additively colored with potassium or cesium. More than ten absorption bands were produced, most of which had previously been found in crystals colored by ionizing radiation. All bands produced by irradiation at or above liquid nitrogen temperature appear to arise from trapped electrons. The most prominent bands in the additively colored crystals are the $F$ band at 642 mμ (liquid nitrogen temperature) and a band at 243 mμ which appears to be due to an impurity. Optically bleaching the $F$ band at 200°K produces bands analogous to the $M$ and $R$ bands in other alkali halides while bleaching at liquid nitrogen temperature yields a broad band identified as the $F^{\prime }$ band. Evidence that the asymmetry of the $F$ band arises from several states of the $F$ center is presented.