The calculation of A-term resonance Raman excitation profiles

A theory of A-term resonance Raman scattering is developed for molecular species with several totally symmetric normal coordinates, the potential minimum in the resonant excited state being shifted only slightly from that in the ground state along any one of these coordinates. The theory is then extended to situations in which more than one excited state contributes to the transition polarizability. Equations are developed by which excitation profiles of totally symmetric fundamentals can be calculated. They are then applied to the mixed-valence complexes ruthenium red and ruthenium brown, and their 1,2-diaminoethane analogues. Relative values for the a 1g displacement parameters are calculated in each case for the situation of resonance with the intense, mixed-valence band of each complex at around 20 000 cm-1.