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

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Abstract
Raman scattering data for neat and mixed crystal IrF6 samples at 77 K are reported. It is found that v 2(eg ) both evidence v5(t 2g ) both evidence non-vanishing Jahn-Teller interactions for the Γ8g (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.