Photo- and Radiation-Stimulated Processes in CsI(Tl) Crystals

The process of radiation-chemical coloration of CsI(Tl) crystals with different carbonate ion contamination has been studied. The presence of carbonate in the CsI(Tl) crystals deteriorates their photo- and radiation stability. Possible reasons for the charge carrier delocalization in CsI(Tl) crystals under exposure to daylight and a role of oxygen-containing impurities in the formation of stable radiation defects have been established. A model of the hole activator color center is suggested. According to the model, the ${\rm Tl}^{2+} {\rm v}_{\rm c}^{-}$ center is a ${\rm Tl}^{2+}$ hole activator center perturbed by a cation vacancy. The electron color centers ${\rm Tl}^{0} {\rm v}_{a}^{+}$ are stabilized not only by the hole color centers of ${\rm Tl}^{2+} {\rm v}_{c}^{-}$ and ${\rm I}_{3}^{-}$, but also by the molecular anions of HCO$_{3}^{-}$ and CO$_{3}^{-}$ formed as a result of the photo- and radio-chemical transformation of CO $_{3}^{2-}$ and OH$^{-}$ ions.