Cross-luminescence of complex halide crystals

Abstract

The cross-luminescence (CRL) resulting from radiative electronic transitions from the mainly anion-related valence band to the uppermost cation core band has been studied in a number of complex halides containing CsCl, RbF, KF, and BaF2. The energy of the CRL photons is determined by the energy difference of the two bands, and the shapes of the spectra reflect the grouping of the molecular orbitals in the clusters involving cations with a hole in the core shell and nearest-neighbour halide ions. For crystals with more than one type of cation, the spectrum reveals information about the 'active' cation which contains the core hole and also about the other cations. Correlations have been established between the local symmetry of the clusters in different crystals and the number and position of the subbands in the CRL spectra.

Luminescence of K1–xRbx CaF3 upon the outermost 3p K+ and 4p Rb+ core ionization

“…Spectral parameters of the CVL, observed for KCaF 3 crystal upon the excitation with synchrotron radiation quanta, are in a good agreement with the literature data on KCaF 3 CVL excited by the electron beam [10]. The excitation threshold of CVL is located at 21 eV corresponding to the ionization of 3p K + core state after transition in X-point of Brillouin zone.…”

“…3, curve 1). This luminescence was observed earlier upon the excitation with the electron beam [10]. The CVL of KCaF 3 crystal reveals the excitation threshold at 21 eV (Fig.…”

Auger-free luminescence due to interatomic p–d transition and self-trapped exciton luminescence in Rb2ZnCl4 crystals

“…A considerable amount of information on AF and STE luminescence is available in simple halides AX such as CsCl and RbF [7][8][9], dihalides BX 2 such as BaF 2 [9][10][11] and trihalides ABX 3 such as CsCaCl 3 and RbCaF 3 [12], where A is a monovalent cation, B a divalent cation and X a halogen anion. Such information, however, is very less in the case of tetrahalide A 2 BX 4 .…”

Thermally and optically stimulated radiative processes in LiBaF3 crystals

“…Two radiation processes observed in undoped LiBaF3 crystals, namely, valence-core band transitions (5.4-6:5 eV) and so-called self-trapped exciton (STE) luminescence (about 4:3 eV) are important for neutron-gamma discrimination (Knitel et al, 1995). It was shown that valence-core luminescence is thermally stable and can be observed above room temperature (Jansons et al, 1993). STE luminescence in LiBaF3 crystals was observed even at 390 K in thermo-stimulated luminescence (TSL) spectrum (Sato et al, 2002), indicating that self-trapped holes (STH) should be stable at least until corresponding temperatures.…”