The luminescence spectrum of ReCl₆^2- doped in various host lattices with antifluorite-type structure

Abstract

The vibrational structure derived from the Γ₇(² T _2g ) → Γ₈(⁴ A _2g ) phosphorescence spectrum at liquid nitrogen temperature of a number of cubic host crystals A₂BX₆ (A = K, Rb, Cs; B = Pt, Sn, Pb, Te; X = Cl, Br) doped with ReCl₆ ^2- has been investigated. The best resolved spectra were obtained for those host crystals absorbing appreciably more of the exciting light than ReCl₆ ^2-. This suggests an energy transfer mechanism from host molecules to the chromophore. The spectral bands are assigned to normal frequencies of the octahedral chromophore, to lattice vibrations and to various combinations. For a complete assignment, vibrational states must be considered which belong to special points in the Brillouin zone other than the zone centre. The zero phonon transitions vary in a definite pattern for host crystals which have closed electron shells. The shifts, which depend more on the cation A⁺ than on the host complex BX₆ ^2-, are discussed by means of ligand field theory.