Hydrostatic Pressure Effects on Self-Trapped Exciton Luminescence in KI

The effect of hydrostatic pressure up to 1.44 GPa upon the luminescence bands associated with self–trapped excitons (STE's) and impurity (Tl+) in KI has been measured at various temperatures. A sapphire anvil cell with helium as a pressure medium is used. The STE luminescence bands show strong blue shift (0.43 eV/GPa for the σ band), which is much larger than the blue shift of the 1s exciton energy (0.16 eV/GPa). The intensities and half-widths of the STE luminescence bands decrease with pressure. These results are discussed on the basis of the exciton-lattice interaction strength depending on hydrostatic pressure.