Circularly polarized Raman spectra of IrCl 62− and FeBr 4−: Spin—orbit induced antisymmetry

Abstract

Circular polarization measurements demonstrate that the depolarized scattering previously observed for the resonance enhanced A 1 vibrational mode of IrCl 6 2− and FeBr 4 − is antisymmetric in character. This effect is attributable to changes in orbital angular momentum via spin—orbit coupling, which introduce antisymmetric components in the electronic tensor associated with the Raman transitions. For IrCl 6 2− spin—orbit coupling in the orbitally degenerate ground state induces anti-symmetry. The ground state of FeBr 4 − is an orbital singlet, and in this case antisymmetry is attributed to a spin—vibronic effect, i.e., vibronic coupling in the spin—orbit manifold of the excited charge-transfer states.