Studies of self-trapped exciton luminescence in KCl

Measurements have been made of the luminescence intensity, lifetime, emission spectra, and linear polarization of self-trapped exciton luminescence in KCl (2.31 eV) at temperatures of 7ᵒK and above. Data are interpreted in terms of an exciton energy-level structure composed of a singlet state approximately 15 meV above a triplet state. The singlet state is populated only by thermal excitation from the triplet. The observed polarization data are consistent with a reorientation of the self-trapped exciton in a state higher than those responsible for the characteristic 2.31-eV luminescence.