Selective laser spectroscopy of SrF{sub 2} crystal doped with Pr{sup 3+} ions
SrF{sub 2} crystals doped with Pr{sup 3+} ions with concentrations corresponding to 0.5, 1.0 and 2.0 wt % of PrF{sub 3} are studied by selective laser excitation. The absorption and luminescence spectra of Pr{sub 3} ions are measured at a temperature of 77 K. Three types of tetragonal centres (C, E, S) with the point symmetry group C{sub 4v} and three types of cluster centres (K{sub 1}, K{sub 2}, K{sub 3}) are found. Energy level diagrams of the {sup 3}H{sub 4}, {sup 3}P{sub 1} and {sup 3}P{sub 2} terms of Pr{sup 3+} ions in SrF{sub 2} crystals are plotted for the tetragonal (C) and cluster optical centres. The lifetimes of the tetragonal C centre [τ(300 K) ∼ 112 μs, τ(77 K) ∼108 μs] and cluster centres K{sub 1} (∼43 μs), K{sub 2} (∼7 μs) and K{sub 3} (∼48 μs) are measured at 77 K for the first time. (laser spectroscopy)