Site selective 4f5d spectroscopy of CaF2:Pr3+

Abstract

Spectroscopic investigations were performed on a single crystal of CaF2 doped with 0.05% Pr3+. Three different Pr3+ sites with different luminescent properties were identified. The 4f2 →4f15d1 excitation spectrum of the first site has a sharp maximum at 221.3 nm. Excitation in the 4f5d bands of this site yields strong 4f5d emissions in the UV/VIS part of the spectrum and also weaker intraconfigurational 4f2 emissions. By comparing the intraconfigurational 4f emissions and their decay times with data from the literature, these 4f5d bands are assigned to transitions on Pr3+ ions on a site with C4V symmetry. The fd excitation spectrum of the second site has a zero phonon line at 223.3 nm. Upon selective excitation in this band, only 4f5d emission is observed. Probably, these 4f5d bands correspond to Pr3+ ions on a Oh site. The third set of 4f5d bands has a 4f5d onset at 208 nm. By comparison of the luminescence spectra of the intraconfigurational 4f2 transitions with literature data, these transitions are assigned to Pr3+ on an L site. Excitation in these 4f5d band yields 1S0 emission followed by emission from the 3P0 state. The present results clarify some contradictions reported in the literature.