Energy transfer in CaF₂:Ce, Mn

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.