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 Tl²⁺v_c ^- center is a Tl²⁺ hole activator center perturbed by a cation vacancy. The electron color centers Tl⁰v_a ⁺ are stabilized not only by the hole color centers of Tl²⁺v_c ^- and I₃ ^-, but also by the molecular anions of HCO₃ ^- and CO₃ ^- formed as a result of the photo- and radio-chemical transformation of CO₃ ^2- and OH^- ions.