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

TL;DR

This study investigates how the local environment affects crossluminescence kinetics in SrF2:Ba and CaF2:Ba solid solutions, revealing longer decay times contrary to expectations and explaining this through core hole migration and transition probabilities.

Contribution

It combines spectral, kinetic, EXAFS, and first-principles calculations to analyze the influence of local environment on crossluminescence in solid solutions, providing new insights into decay mechanisms.

Findings

Longer CL decay times in SrF2:Ba and CaF2:Ba compared to BaF2.

Discrepancy between expected and observed decay acceleration explained by core hole migration.

Decreased optical transition probability between Ba(5p) states and valence band in 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.