The scattering of light by a spheroidal metal particle has been newly treated by use of the technique of the multipole expansion of radiation fields from the induced polarization and the associated current and magnetization, which are now considered as radiation sources. The relation between the polarization and the incident field is most simply obtained by using the long-wavelength approximation and a radiation-damping correction. The various orders of electricand magnetic-multipole coefficients of scattered fields have been separately calculated. Part of our calculated results confirm and thus justify the well-known features that the electric-dipole term gives the dominant contribution and that the magnitudes of multipole coefficients decrease monotonically with the increasing-order number of the multipoles. Some new features concerning the accuracy and the limitation of the radiation-damping correction are discussed against the depolarization factor of the spheroid. For a small sphere, the results reduce to the famous Rayleigh scattering, as expected. Results for larger spheres are compared with those of an exact electrodynamical calculation.

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The enhancement of Raman scattering from a CN molecule adsorbed on the tip of one of a 2-D array of Ag spheroids has been newly calculated using the full dipole fields. Results are compared to the corresponding experimental data from the lithographically produced Ag microspheroids. While the r−1 term is small in our specific configuration of molecule-spheroids arrangement, the r−2 term of the full dipole fields is found to contribute about the same amount to the excitation profile of the Raman enhancement as the conventional r−3 term. We also find a kind of spectral fluctuation in the Raman excitation profile and have demonstrated it as due to the interference between the r−2 and r−3 fields.

The surface enhanced Raman scattering as observed from molecules on Ag and Au arrays of microspheroids has been newly treated with suitable Gaussian distributions of axial ratios of these microspheroids. Calculated results for the enhancement factor features such as magnitude, peak position, and linewidth, all agree satisfactorily with existing experimental data, suggesting a possible physical mechanism for the Raman scattering.

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