Effect of local environment on crossluminescence kinetics in SrF2:Ba and CaF2:Ba solid solutions

Abstract

Spectral and kinetic properties of extrinsic crossluminescence (CL) in SrF2:Ba (1%) and CaF2:Ba (1%) are compared with those of intrinsic CL in BaF2 and are analyzed taking into account EXAFS data obtained at the Ba LIII edge and results of first-principles calculations. The CL decay time was revealed to be longer in SrF2:Ba and CaF2:Ba compared to BaF2. This fact contradicts the expected acceleration of luminescence decay which could result from an increased overlap of wave functions in solid solutions due to shortening of the Ba-F distance obtained in both EXAFS measurements and first-principles calculations. This discrepancy is explained by the effect of migration and subsequent non-radiative decay of the Ba (5p) core holes in BaF2 and by decreasing of the probability of optical transitions between Ba (5p) states and the valence band in SrF2:Ba and CaF2:Ba predicted by first-principles calculations.