Pressure-induced absorption spectra change in alkali halide phosphors: mutual mixing between excited states

Abstract

An apparatus has been developed which permits optical measurements up to 30 kbar at 1.5K using a piston-cylinder-type high-pressure cell. Using this apparatus, studies of the hydrostatic pressure effects of absorption spectra of KI and KBr doped with Tl+ or In+ have been made up to 10 kbar. Under high pressure, a mutual mixing occurs due to the electron-lattice interaction between the excited states corresponding to the A, B, C and D absorption bands, even at low temperatures, resulting in the give-and-take of the absorption intensity between these absorption bands. To explain the mutual mixing, the pressure dependence of the electron-lattice coupling is taken into account. The pressure variation of the A band shape is also discussed in connection with the pressure dependence of the electron-lattice coupling constants.