Decay kinetics of exciton luminescence from two coexisting off-center configurations in KCl:I

Abstract Short-lived components of the ns time range were found in the luminescence decays of two coexisting off-center excitons (types II and III) in KCl:I. Temperature dependence of the intensities and lifetimes were analyzed by means of a three-level energy diagram for the adiabatic potential energy surfaces (APES's) of the lowest singlet and triplet states. We found that the potential barrier between the two configurations is higher on the singlet APES than on the triplet APES. An exchange energy between the singlet and the triplet was estimated to be ∼92 meV at the type II configuration while 32 meV at the type III configuration. This provides a direct evidence for the anticipation that the exchange energy must be appreciably enhanced at a weakly off-centered configuration [9].