Resonant Cancelation of Raman Scattering from CdS and Si

Abstract

A pronounced decrease in the TO Raman scattering efficiencies of CdS has been observed as the incident photon energy approaches the direct-energy gap. Previous resonant Raman measurements have shown only monotonically increasing efficiencies. A decrease of the $F_{2g}$ mode in Si has also been observed as the resonance with the indirect-energy gap is approached. The observed decreases in CdS and Si can both be accounted for by extending Loudon's theory to include a destructive interference between the resonant and nonresonant contributions to the Raman scattering amplitudes.