Formation of anion vacancies in the course of dissociation of thermally excited triplet excitions in a KI crystal

The method of time-resolved optical spectroscopy was used in a study of the dynamics of formation and evolution of anion vacancies (α color centers) in a KI crystal irradiated with electron pulses of 10 −8 s duration and E = 0.25 MeV energy. A delayed rise of the number of α centers after the end of irradiation was observed in the temperature range 110-140 K synchronously with relaxation of triplet self-trapped excitons. The results of a comparative study of the temperature dependences of the yield and the rate of relaxation of the a centers and self-trapped excitons indicated that thermally activated transformation of these excitons from the lowest relaxed 3 Σ u + state into pairs of spatially separated α and I centers occurred in the investigated KI crystal. The yield of the a centers per one self-trapped exciton was found to be 0.3