Transient photoluminescence and excited-state optical absorption in trigonal selenium

Abstract
The results of an investigation of the transient mid-gap photoluminescence (PL) and photo-induced optical absorption in trigonal Se are presented. Direct evidence is found for a barrier of 35±5 meV to trapping of free excitons at the PL center. All the features of the PL, including the high-temperature nonradiative decay, can be explained with a simple model in which electron-phonon coupling in the excited state of the PL center, although very strong (S=50), is nonetheless linear.