Generation of Free Excitons by Optical Excitation of Self-Trapped Excitons in KI

Abstract

Luminescence emitted by photo-excitation of self-trapped excitons in KI has been studied. It is found that the luminescence due to free excitons is generated when the self-trapped excitons at the lowest triplet state from which the π-luminescence is emitted is excited with 2.5 eV photons. Furthermore studies of the dependence of the increment of the σ-luminescence and the decrement of the π-luminescence induced by photoexcitation revealed that the collisions between free excitons and the self-trapped excitons annihilate the former.