Electromagnetic theory of enhanced Raman scattering by molecules adsorbed on rough surfaces

Abstract

A theory for surface enhanced Raman scattering (SERS) is developed. Effects due to realistic surface geometry and dielectric properties are included. Three sources of enhanced Raman scattering are noted: the image dipole enhancement effect, the increase of local field (’’lightning rod’’ effect), and the resonant excitation of surface plasmons. The surface is modeled as a hemispheroid protruding from a conducting plane, although other models are considered. The spherical limit is discussed in some detail and molecular orientation effects are considered. Cross sections for Mie, Rayleigh, and Raman scattering are derived.