LUMINESCENCE FROM ICL- VK-CENTER-ELECTRON RECOMBINATION AND LOCALIZED EXCITON DECAY IN KCL-I

Recombination luminescence is observed in x-irradiated KCl: I at low temperatures and is shown to originate from the recombination of an electron with the self-trapped hole of the mixed-halogen VK center, ICl-. In pulse-annealing experiments, the two observed emission bands, at 470 and 365 nm, scale in intensity with ICl- concentration, and following polarized orientation of the ICl- centers, a partial π polarization of the more intense 470-nm emission is found. These two recombination-emission bands appear identical to the emission observed by direct optical excitation of the iodine ions in KCl: I. Thus, in the mixed alkalihalide crystal KCl: I, analogous to the pure-crystal case, optical excitation of the impurity iodine ion leads to formation of a relaxed excited-state configuration resembling a mixed diatomic molecule ICl-(ICl- VK center+electron). © 1968 The American Physical Society.