Lifetime of the Excited I- Center in KCl

The lifetimes of two excited states of iodine centers in KCl single crystals were measured between 15 and 300°K, following flash excitation. Previous and new results of the fluorescent yield of these same emission processes are presented for comparison. At low temperatures the radiative lifetime is 1.7×${10}^{-4\mathrm{}}$ sec and the yield 100%±50% for the blue-green emission process; for the ultraviolet emission the lifetime is 1.3×${10}^{-7\mathrm{}}$ sec and the maximum yield 70%±35%. In an intermediate temperature range, the radiative lifetime starts to decrease whereas the yield stays constant. At still higher temperatures, the lifetime and the fluorescent yield both decrease rather sharply.