Intrinsic Luminescence in KBr Crystals between 1.8 K and 80 K

Intrinsic luminescence and optical absorption from the triplet state of the self trapped exciton in KBr crystals have been observed by a pulsed electron beam and by a N 2 laser. The π emission at 2.28 eV decays with two components of ∼3 ms(τ S ) and 100 µs(τ F ) at 1.8 K. τ F component arises from a transition from B u (a combined state of B 3 u and B 2 u ) to A g , and τ S component from A u → B u →A_g i n t h e s e l f t r a p p e d e x c i t o n a s t h o s e i n K I r e p o r t e d b y f i s c h b a c h et al . T h e e n e r g y s e p a r a t i o n b e t w e e n B_u a n d A_u i s 1.6 m e V . I n a d d i t i o n t o t h e a b o v e , t e m p e r a t u r e d e p e n d e n c e o f t h e y i e l d o f t h e 2.28 e V e m i s s i o n a n d o f t h e s e l f t r a p p e d e x c i t o n s a t t h e t r i p l e t s t a t e i s d i s c u s s e d i n c o n n e c t i o n w i t h t h e F c e n t e r f o r m a t i o n .