Intensity distribution in the progressions of vibronic transitions of metal-ion complexes

Abstract

Abstract The intensity distribution of the vibrational progressions t 1u + na 1g and t 2u + na 1g in a vibronically induced transition has been investigated using ReCl6 2- doped in Rb2TeCl6 and Cs2TeCl6 as an example. It has been shown that this distribution can be expressed in condensed form by an intra-molecular distribution function I 0 (n, ΔΓ, βΓ) where n denotes the member in the progression and ΔΓ and βΓ represent changes in equilibrium position and frequency, respectively, of the mode Γ following an electronic transition. For Rb2TeCl6 : Re4+ the experimental data are best fitted to the theory with the parameters Δ = 0·37 and β = 0·995, and for Cs2TeCl6 : Re4+ Δ = 0·32 and β = 0·995. The Δ-parameters correspond to a change in the nuclear equilibrium configuration of the metal-ligand distances by 0·015–0·020 Å on excitation of the molecule to 2 T 2g . The detection of an eg vibronic line and its combinations eg + na 1g is explained by a Jahn-Teller distortion in the 4 T 2g excited state.