Abstract

A model for Raman scattering by a molecule adsorbed at the surface of a spherical particle is articulated by treating the molecule as a classical electric dipole. This follows Moskovits’s suggestion [ J. Chem. Phys. 69, 4159 ( 1978)] and the experiments by Creighton, et al. [ J. Chem. Soc. Faraday Trans. II , 75, 790 ( 1979)] that such a system may exhibit SERS similar to that at roughened electrode surfaces. The molecule is stimulated by a primary field comprised of the incident and near-scattered fields. Emission consists of the dipole field plus a scattered field, each at the shifted frequency. Addition of feedback terms between the dipole and the particle makes only a negligible contribution to the fields. For pyridine adsorbed at the surface of a silver sphere, the 1010-cm⁻¹ band is enhanced by ~10⁶ if the radius is much less than the wavelengths and the excitation wavelength is ~382 nm, a wavelength for which the relative refractive index of silver is close to $m=\sqrt{2i}$. Detailed results are given for the effect, upon the angular distribution and the polarization of the Raman emission, of particle size, distance from the surface, excitation wavelength, and location of the molecule upon the surface. These results simulate those observed at roughened silver electrodes and suggest that the mechanism of SERS at those electrodes may resemble the electromagnetic mechanism elucidated here. We predict that comparable effects should be observed for fluorescent scattering.

© 1980 Optical Society of America

Surface enhanced Raman scattering (SERS) by molecules adsorbed at spherical particles: errata

Milton Kerker, Dau-Sing Wang, and H. Chew
Appl. Opt. 19(24) 4159-4174 (1980)

Enhanced Raman scattering at the surface (SERS) of a spherical particle

D.-S. Wang, H. Chew, and M. Kerker
Appl. Opt. 19(14) 2256-2257 (1980)

Simple model for estimating the electromagnetic enhancement in surface-enhanced Raman scattering from molecules adsorbed onto metal particles coated with overlayers

Cherry A. Murray
J. Opt. Soc. Am. B 2(8) 1330-1339 (1985)

Raman and fluorescent scattering by molecules embedded in dielectric spheroids

Dau-Sing Wang, Milton Kerker, and Herman W. Chew
Appl. Opt. 19(14) 2315-2328 (1980)

Raman and fluorescent scattering by molecules embedded in dielectric cylinders

H. Chew, D. D. Cooke, and M. Kerker
Appl. Opt. 19(1) 44-52 (1980)