Raman scattering by high-density dispersions. I. Formulation of theory and application to a pair of coated particles

Publisher Website
Google Scholar
Abstract
The methods developed in our earlier papers, dealing with Raman scattering from small isolated, spherical particles, uniformly coated with radially uniaxial molecules, are extended to include scattering driven by applied multipolar fields. Such fields are generated by the action of the incident electromagnetic radiation on extraneous material, such as other particles belonging to the same high-density dispersion. In this paper we treat inelastic scattering associated with the Raman dipole matrix elements of the adsorbed molecules ignoring other contributions. Analytical expressions are developed for calculating the primary Raman–Stokes moments given the amplitudes of the applied multipolar fields. As a test of the practicability of the procedure, a full calculation for parallel polarization has been performed for two identical contacting, CO-coated Ag particles oriented with their line of centers parallel to the direction of polarization of the incident radiation. For this case, the effect of interparticle coupling is to broaden and intensify the excitation spectrum, extending the region of intense Raman scattering to much lower frequencies. Intensity enhancements approaching 106 are calculated for frequencies as low as 80% of the single-particle surface-plasmon resonance frequency.