A number of unusual electromagnetic scattering effects for magnetic spheres are described. When e = It, the backscatter gain is zero; the scattered radiation is polarized in the same sense as the incident radiation. In the smallparticle (or long-wavelength) limit, conditions are described for zero forward scatter, for complete polarization of scattered radiation in other directions, and for asymmetry of forward scatter to backscatter. The special case in the small-particle limit of m = 1, i.e., ,u = 1/e, provides interesting special instances of complete polarization and forward-scatter-to-backscatter asymmetry.

A solution is given for the problem of the scattering of plane electromagnetic waves from a sphere with a concentric spherical shell. The solution is general, and under appropriate conditions is reduced to the well-known solution for scattering from a single sphere.

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 ~10(6) 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 = radical2i. 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.

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