Nonradiative Transition Processes between the Relaxed Excited States of Ag- Centers Doped in KI Crystals

Decay kinetics and intensities of the luminescence bands for Ag- centers doped in KI single crystals have been investigated over a wide temperature range between 5 and 310 K. The Ag- centers doped in KI exhibit a broad and largely Stokes-shifted C* luminescence band at about 1.60 eV in addition to the A' and C' luminescence bands, whose peaks are 2.65 and 3.67 eV, respectively. The luminescence intensities of these bands change with temperature while complementing each other. Decay times of the luminescence decrease in the temperature range where the luminescence diminishes with increasing temperature. The temperature evolutions of the decay times and the intensities of the luminescence are analyzed on the basis of a configuration coordinate model including the thermally activated nonradiative transitions among the relaxed excited states. From the analysis results, the parameters characterizing the respective nonradiative transitions are determined.