Surface phonon induced Raman scattering: A new mechanism for intense inelastic scattering

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Abstract
This paper forms the third in a series on the optical properties of a system consisting of a uniform, radially uniaxial coating of molecules on a small isotropic sphere. In this paper, the induction of Raman activity in a coated metal sphere by the fields generated by the coupled surface phonon modes of the coating is considered. Thus, the surface phonon modes induce surface plasmons in the metal that result in its polarizability being modulated. The phenomenon, which requires dipole active rather than Raman active molecular modes to be operative, we have termed surface phonon induced Raman scattering (SPIRS). Scattering intensities predicted via SPIRS and surface enhanced Raman scattering (SERS) have been compared for CO on a spherical silver particle. That for SPIRS is found to be of the order of or greater than that for SERS, depending on exactly how the surface region of the metal sphere is modeled. Some predictions based on SPIRS are reminiscent of data previously assigned to SERS but not explained by current models.