Luminescence spectra and electronic levels of osmium(IV) in cubic and quasi-tetragonal symmetry

Abstract Power luminescence spectra of Os(IV) doped in Rb 2 SnCl 6 (cubic) and K 2 SnCl 6 (mono-clinic) at 10 K have been measured. Three spectral regions attributable to transitions into the spin-orbit components of the 3 T 1 g ground term have been investigated by Lorentzian band analyses. Vibronic selection rules and relative band intensities for K 2 SnCl 6 : Os 4+ , in which the site symmetry of osmium ions is almost tetragonal, indicate that the spin-orbit levels resulting from 3 T 1 g have the order Γ 1 4 3 5 . Ligand field results including complete configuration interaction calculated with appropriate sets of parameters are in accordance with this sequence. A band was detected in the lattice mode region which was significantly altered in frequency upon temperature variation (10–120 K). This transition has been explained by a combination of two photons, involving a promoting mode and a soft mode, which induces the phase transition of the host crystal at 255 K.