Jahn–Teller effect in the Γ8(2T2g, t 32g) state of ReBr 2–6

Abstract

The Γ₈,Γ₇(²T_2g, t³_2g)→Γ₈(⁴A_2g, t³_2g) luminescence spectrum of the ReBr^2–₆ ion in several cubic host lattices has been measured at temperatures down to 6 K. For both transitions the luminescence may be analysed into progressions in the α_1g and ε_g stretching vibrations of the complex ion based on the 2τ_1u and τ_2u vibronic origins, but the progressions in the τ_g mode are two orders of magnitude stronger in the T₈→ T₈ transition than in the Γ₇→Γ₈ transition. This is strong evidence for a Jahn–Teller effect in the Γ₈(²T_2g) state of ReBr^2–₆.