Temperature-dependent luminescence spectra and lifetime measurements of octahedral Se(IV) and Te(IV) hexahalogeno coordination compounds

Abstract

Emission spectra and lifetime measurements of microcrystalline A 2SeCl 6, A=Cs, Rb and Cs 2TeX 6, X=Cl, Br excited in the lowest electronic transition are reported for the temperature interval from T=1.9 to 240 K. The results are explained by a model which considers spin-orbit coupling, electron-electron interaction and the electron-phonon coupling (Jahn-Teller effect) of the complex molecule MX 6 2−. Evaluation of the measured data indicates that the lowest excited states Γ 1 and Γ 4 resulting from the sp electron configuration differ by only about 110 and 95 cm −1 for the Se(IV) and Te(IV) compounds, respectively. For the SeCl 6 2− complex, emission only from Γ 1 is observed at temperatures below 2.1 K. The emission properties of octahedrally coordinated s 2 ions can be explained by simple models including kinetic aspects. The relative orders of magnitude calculated for the decay rates correspond to predictions obtained from selection rules.