抄録
Recombination luminescence (π and σ) in KI has been observed with red light stimulation after or during exposure at 78 K to UV light. Using a pulse annealing technique, the hopping migration of VK centers is studied by monitoring the decrease of the photostimulated luminescence as a function of time and temperature. It is confirmed that the long-range diffusion of VK centers is characterized by a thermal activation energy of 0.27 eV. When a preexposed sample is warmed to 124 K, subsequent red irradiation at 78 K is found to stimulate the Ex (3.02 eV) emission in place of the π emission. This can be regarded as evidence in favor of the extrinsic nature of the Ex emission. Thermal quenching of the Ex, π and σ emissions is also investigated in detail under UV light excitation. On the basis of these results, we discuss the nonradiative decay process of the self-trapped excitons in KI.
