Origin of asymmetric scattering tensors of normal modes in electronically degenerate states

Abstract

A discussion is given of the form of the scattering tensor of all possible normal modes in all possible electronically degenerate states of the important crystallographic point groups with doubly and triply degenerate representations. Arguments are put forward that asymmetric tensors do not contribute to the intensity of totally symmetric modes in electronically degenerate states. However, such tensors can contribute to the intensity of some of the other modes. The form of the scattering tensor is obtained from a study of corresponding transitions if the symmetry of the molecule is lowered so that degeneracies are removed. This lower symmetry situation is so chosen that it belongs to a group which is the subgroup of highest symmetry of the group which describes the symmetry of the molecule having degenerate electronic states.