The optical surface modes of metal spheres

Abstract

A theoretical study of optical surface plasmon modes of metal spheres is made within the framework of a free-electron spatially dispersive dielectric function model which includes retardation effects. Dispersion equations for homogeneous and inhomogeneous spheres are derived for the lth spherical harmonic. The radiative properties of the modes are investigated as a function of l and surface structure which is included by means of a double step-function profile. The real part of the frequency has the same magnitude, and trend with sphere radius, as the current experimental results.