SURFACE-PLASMON MODES OF SPHERICAL VOIDS IN IRRADIATED METALS

The surface plasmon modes of spherical voids in metals modeled by a free-electron gas are calculated within a hydrodynamic formulation. Spatial dispersion, retardation, and surface electron density variation are included. A sharp-surface model is considered first and it is shown that the modes are non-radiative. A novel matrix method is used to discuss the sensitivity of the results to the use of different surface density profiles. It is shown that the interplay between surface inhomogeneity and spatial dispersion always results in a mode in the near neighbourhood of the sharp-surface mode. There are, however, other structure-induced modes which are well-separated from the sharp-surface results. The l = 0 breathing mode is affected by retardation and surface structure but is unaffected by spatial dispersion. © 1979.