Cation size dependence of phosphorescence lifetime of Eu2+ doped alkali halide crystals

Abstract Phosphorescence lifetimes of europium doped alkali halide crystals have been measured and compared with each other. The lifetime values resulted to be more influenced by the cation size following an increasing order from Li to Rb. The effect of covalency decrease from Li to Rb and the corresponding mixing of 4f7 and 4f65d states of europium ions suggests an influence of the low lying 6 P 7 / 2 level of the 4f7 electronic configuration on the relaxation from the 4f65d excited state to the 8 S 7 / 2 ground state.