LASER SITE-SELECTIVE SPECTROSCOPY OF TB3+ IONS IN CAF2 AND SRF2

From a combination of polarized laser selective excitation spectroscopy and infrared absorption measurements, sets of energy levels have been established for the Tb3+ C4v centers present in as grown CaF2:0.05%Tb3+ and SrF2:0.05%Tb3+ crystals. After hydrogenation, at least five new hydrogenic centers are created whose varied bleaching behavior includes that of a center whose intensity increases on irradiation into its excitation transitions. Measured 5D4 multiplet fluorescence lifetimes of all the centres are similar for hydrogen and deuterium varieties indicating essentially radiative lifetimes. As the bleaching effects are more pronounced for the H- variety of a given hydrogenic center, the bleaching of the centers requires any involved local mode phonons to be created through non-radiative decay processes from the lower 7F multiplets.