Polarized electronic absorption spectra of the trigonal crystal K₂ReF₆

Abstract

Linearly polarized (α, σ, π) electronic absorption spectra have been measured on trigonal crystals of K₂ReF₆ at temperatures down to 4·2 K. Almost all of the expected magnetic dipole electronic transitions associated with the t _2g /³ configuration have been identified between 9000 and 20000 cm^-1. Each electronic transition shows detailed electric dipole vibronic structure which has been analysed. There is evidence for a moderate Jahn-Teller coupling to v ₂ and v ₅ modes within the trigonal components of the Γ₈(² T _1g ) and Γ₈(² T _2g ) states and for vibronically enhanced resonance coupling between nearby states. The results are compared with previous studies on Re⁴⁺ complex ions and with IrF₆.