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 (K₁, K₂, K₃) are found. Energy level diagrams of the ³H₄, ³P₁ and ³P₂ terms of Pr³⁺ ions in SrF₂ crystals are plotted for the tetragonal (C) and cluster optical centres. The lifetimes of the tetragonal C centre [τ(300 K)∼112 μs, τ(77K)∼108 μs] and cluster centres K₁ (∼43 μs), K₂ (∼7 μs) and K₃ (∼48 μs) are measured at 77 K for the first time.