Theory of resonant Raman enhancement of a forbidden phonon in Cu2O

A theoretical calculation is given of the frequency dependence of resonant enhancement of Raman scattering by the normally forbidden 109 cm^?1 (Γ12-) optic phonon for incident frequencies near the 1s Yellow exciton energy. The theoretical results are in good agreement with recent experiments. This gives support to a quadrupole-dipole mechanism with Yellow-Blue exciton scattering in the intermediate state.