The unusual temperature dependence of the Eu~(2+) fluorescence lifetime in CaF_2 crystals

摘要

Fluorescence lifetimes of Eu~(2+) doped in CaF_2 are measured at various temperatures between 4 and 450 K. The lifetime increases between 100 and 320 K, in contrast to the usual lifetime-temperature dependence. At higher or lower temperatures, the lifetime decreases with increasing temperature. This phenomenon is explained by simulation of the energy levels and lifetimes of low-lying 4f5d states involved in the fluorescence.