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 SrF 2 :Ba(1%) and CaF 2 :Ba(1%) are compared with those of intrinsic CL in BaF 2 and are analyzed taking into account EXAFS data obtained at the Ba L III edge and results of first-principles calculations. The CL decay time was revealed to be longer in SrF 2 :Ba and CaF 2 :Ba compared to BaF 2 . 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 BaF 2 and by decreasing of the probability of optical transitions between Ba (5p) states and the valence band in SrF 2 :Ba and CaF 2 :Ba predicted by first-principles calculations.

New ultrafast scintillators with core valence luminescence: Cs2MgCl4 and Cs3MgCl5

“…57 This relationship has been discussed in other works as well. 31,58,59 To determine whether the trend holds for the A 3 MX 5 -type (space group I 4 / mcm) and A 2 MX 4 -type (space group Pnma) compounds, decay constants and average Cs-Cl bond lengths were compiled and are listed in Table 2 along with those of CsCl and CsMgCl 3 . It should be noted that the AX and AMX 3 -type compounds are a simpler case given that only one crystallographic site exists for Cs ions whereas two sites exist in the A 2 MX 4 -type and A 3 MX 5type compounds (as discussed in Section 3.1).…”

“…In an investigation of impurity-induced CVL in CaF 2 :Ba and SrF 2 :Ba, Terekhin et al also did not observe the expected acceleration of decay time despite the smaller Ba-F distances in the doped compounds compared to BaF 2 and point out that the probability of optical transitions is not only determined by the CVL-active cation to halogen anion distance, but also by the shape of the respective wave functions. 59 Pulse height spectra for small-sized crystals of Cs 2 MgCl 4 and Cs 3 MgCl 5 are shown in Fig. 8.…”