Optical properties of molecules forming a uniform, uniaxial layer on a small, isotropic sphere

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Abstract
This project was inspired by the widespread use of the properties of coated spheres in modeling the dielectric and spectroscopic behavior, including surface enhanced Raman spectroscopy, of a variety of dispersed systems. In this paper the self-polarizing contributions to the absorption and elastic scattering properties of a coated sphere are obtained in the large wavelength limit, or dipole approximation, in which the coating is treated as a polarizable, uniaxially anisotropic, shell with the local optic axis directed radially. Numerical calculations for CO on Ag are provided to illustrate some of the phenomena predicted by the equations. Of particular interest are the dependence of the absorption band for CO stretch upon particle size, surface coverage, and molecular orientation, and the dependence of the surface plasmon resonance absorption on particle size and coverage. Some limitations of the model are examined.