FLUORESCENCE DECAY-RATES OF X2UO2CL4 X = CS, RB, AND K

Fluorescence of alkali uranyl chloride single crystals originates from close-lying doublet levels. The fluorescence decay contains two different decay rates. One rate describes the relaxations of the pure crystal, whereas the other is related to relaxations of impurities or defects in the crystal. The temperature dependence of the two decay rates has been measured. Moreover, it can be explained by assuming that the fluorescent doublet is always in thermal equilibrium with a higher electronic level E//x which has a fast relaxation time. Comparison between measurement and theory of the temperature dependence of the decay rates yields the energy separation DELTA E between the fluorescent doublet and E//x. Furthermore, DELTA E can be correlated with other spectroscopic measurements.