Selection rules and Raman spectrum of a molecule with a degenerate ground state and zero spin-orbit coupling: VCl4

Two interesting features can normally be expected in the Raman spectrum of a molecule with a degenerate electronic ground state (i) the contribution of asymmetric or even antisymmetric tensors to the Raman intensity (ii) lifting of the electronic degeneracy due to Jahn-Teller distortion. The experimental data and discussion on VCl₄, presented here, show that this molecule does not show any deviations in the Raman selection rules. Further, its Raman spectrum closely resembles that of TiCl₄ which also has T_d geometry but a nondegenerate singlet ground state. This suggests the absence of any static Jahn-Teller distortion in VCl₄. However, we have observed a broadening of the ν₂ band of VCl₄ over TiCl₄ and we attribute this to a possible dynamic Jahn-Teller splitting.