Comparison of Raman scattering from local and coupled surface phonon modes of small uniformly coated spheres

Abstract

Building on our recent paper on the optical properties of molecules forming a uniform, uniaxial layer on a small isotropic sphere, the present paper extends the treatment to include Raman scattering from both local modes and the coupled or surface phonon modes of such a system. As with the earlier paper, the treatment is restricted to the large wavelength approximation. While Raman inactive molecular modes can result in Raman active phonon modes, the present paper considers only those Raman active phonon modes that are connected with Raman active molecular modes. For such phonon modes, the field enhancement factors for the scattered wave are identical in form to those for the incident wave, derived in our recent paper, but differ significantly from those for local modes. Calculations are presented for CO and benzene on silver particles.