Raman scattering of neat and mixed crystals of IrF₆ : the Jahn-Teller interaction in the ground state

Abstract

Raman scattering data for neat and mixed crystal IrF₆ samples at 77 K are reported. It is found that v ₂(e_g ) both evidence v₅(t _2g ) both evidence non-vanishing Jahn-Teller interactions for the Γ_8g (⁴ A _2g ) ground state. The linear Jahn-Teller parameters for these modes are D ₂⩽0.·001 and D ₅=0·02. The v ₅ Jahn-Teller interaction is large enough to quench an expected exciton splitting of ∼20 cm^-1 almost completely. The v ₂ Jahn-Teller interaction is small enough so that exciton interactions predominate; however, normal v ₂ k=0 sharp line exciton structure is not observed. Anomalous phonon behaviour is observed and discussed with respect to other hexafluoride phonon data. The non-Jahn-Teller active modes v ₁, v ₃, v ₄, v ₆ are found to behave in a fashion consistent with other members of this series.