Luminescence spectra and relaxation processes of ReCl 2–6 in cubic crystals

Abstract

The Γ₇(²T_2g, t³_2g)→Γ₈(⁴A_2g) luminescence spectra, emissive life-times, excitation spectra and Γ₈(⁴A_2g)→Γ₆(²T_1g, t³_2g), Γ₇Γ₈(²T_2g, t³_2g) absorption spectra of ReCl^2–₆ in A₂SnCl₆(A = K, Rb, Cs) and K₂PtCl₆ have been measured between 4 and 300 K. The absorption and luminescence spectra of each transition are dominated by three vibronic origins due to the ν₆, ν₄ and ν₃ localised internal modes of the ReCl^2–₆ ion. The detailed structure near these origins shows features due to the coupling of band modes of the host to the localised modes. Every feature and the absorption and emission spectra of K₂SnCl₆: ReCl^2–₆ is doubled due to the low-temperature phase transition in the host. For the K₂PtCl₆ host the ReCl^2–₆ ion can be excited by energy transfer from the PtCl^2–₆ ion but the kinetics of the transfer are unusual.