Selective laser spectroscopy of SrF2 crystal doped with Pr3+ ions

SrF2 crystals doped with Pr3+ ions with concentrations corresponding to 0.5, 1.0 and 2.0 wt % of PrF3 are studied by selective laser excitation. The absorption and luminescence spectra of Pr3 ions are measured at a temperature of 77 K. Three types of tetragonal centres (C, E, S) with the point symmetry group C-4v and three types of cluster centres (K-1, K-2, K-3) are found. Energy level diagrams of the H-3(4), P-3(1) and P-3(2) terms of Pr3+ ions in SrF2 crystals are plotted for the tetragonal (C) and cluster optical centres. The lifetimes of the tetragonal C centre [tau(300 K) similar to 112 mu s, tau(77 K) similar to 108 mu s] and cluster centres K-1 (similar to 43 mu s), K-2 (similar to 7 mu s) and K-3 (similar to 48 mu s) are measured at 77 K for the first time.