Anomalous magnetic field-induced birefringence in molecular systems with the Jahn-Teller effect

Abstract

It is shown that spherical-top molecules in orbitally degenerate states possess anomalous anisotropy of electric and magnetic properties leading to temperature-dependent birefringence induced by a static magnetic field. The Cotton-Mouton constant mC is expressed in terms of anisotropic tensors of the molecular polarizability, magnetic susceptibility, magnetic moment and magneto-electric hyperpolarizability. The resulting temperature dependence of mC is different from that (quadratic in T -1) expected without the Jahn-Teller effect. This difference is defined by introducing in this paper temperature-dependent reduction factors of electronic operators, which at low temperatures coincide with the usual ones. Reduction factors are calculated for systems with G 3/2 ground electronic terms. For these cases approximate analytical expressions are obtained taking into account the vibronic coupling with e and t 2 vibrations. Numerical estimation of the expected Cotton-Mouton constant in the case of the ReF6 molecul...