Inelastic Mie scattering from rough metal surfaces: Theory and experiment

Abstract

A theory for inelastic Mie scattering from rough metal surfaces or metal sols is proposed. A resonant excitation of a localized dipolar plasmon can enhance the cross section, and experimental data relating to the phenomenon in silver and copper are presented. Two distinct effects are noted. One is inelastic light scattering from the rough metal surface or bare metal sol. The other is related to Reyleigh scattering from adsorbed molecules as modified by the presence of the substrate. Both involve frequency shifts determined by the characteristic mechanical vibrations of the metal. A striking feature of this inelastic Mie scattering is that for a distribution of particle sizes and shapes the frequency shift changes as the incident laser frequency is changed or as the index of refraction of the surrounding medium is changed. Inelastic Mie scattering is shown to yield important information on the surface roughness required for the observation of surface-enhanced Raman scattering.