Irreducible analysis of Raman spectra for all crystal point groups

Abstract

Techniques for the optimal and maximal extraction of information by Raman scattering experiments are investigated. All optical interactions are assumed to be electric dipole. For each crystal point group symmetry, a minimal set of choices of experimental arrangement (i.e. choice of polarisation vectors for incoming and outgoing light beams, scattering geometry etc.) is given, together with the transformations necessary to determine the irreducible parts of the spectrum in each of several bases. The more detailed tables are presented as a supplementary publication, SUP 70031. While valid for all crystal point groups, they are restricted to the case of time-reversal-invariant scattering interactions, and also to symmetric scatterers. The latter restriction includes systems which may have an antisymmetric part to the scattering amplitude, but in which the scattering intensity is unchanged by interchanging the incoming and outgoing polarisation vectors. Circular polarisation studies are necessary for a complete analysis of any system. However, the conventional 90 degrees and 180 degrees scattering geometries are adequate. Related symmetries of the Mueller matrix of the scatterer are also analysed.