RADIATIVE AND NONRADIATIVE RELAXATION MEASUREMENTS IN CE3+ DOPED CRYSTALS

Radiative and nonradiative transition rates from the lowest excited Ce3+ 5d level in a series of cerium doped oxide and fluoride crystals (Ce3+:LaF3,Ce3+:CaF2,Ce3+:YLiF4,Ce3+:Y3Al5O12, and Ce3+:YAlO3) have been determined by measuring the Ce3+5d --> 4f fluorescence lifetime as a function of sample temperature. The onset of the thermally induced nonradiative transitions occurs for temperatures T* between 300 and 900 K depending on the host crystal. At temperatures lower than T*, there is an additional but much weaker temperature dependance of the radiative lifetime. Analysis of the radiative lifetime shows that the radial integral ]4f\r\5d} varies by about 20% from the mean value of 0.30 angstrom among the set of five host crystals, and is a factor of about 1.5 smaller than the free-ion value.