Energy transfer in CaF2:Ce, Mn

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Abstract
Crystals of CaF2 containing different concentrations of Ce3+ and Mn2+ ions were investigated by means of optical absorption and photoluminescence. The results suggest the preferential pairing of the Mn2+ ions with Ce3+ ions in tetragonal sites (i.e. sites in which the Ce3+ ion is locally compensated by an F-interstitial in a (100) direction). At these centers efficient energy transfer from Ce3+ to Mn2+ takes place. However, a different behavior is noted when the specimens are irradiated. Measurements of X-ray- induced luminescence and thermoluminescence reveal that energy transfer does not appear to play an influential role in these latter processes. Instead of tetragonal sites, other Ce3+ centers, particularly cubic and trigonal photochromic centers, appear to dominate the X-ray-induced luminescence and the thermoluminescence.