Effect of hydrodynamic dispersion of the metal on surface plasmons and surface-enhanced phenomena in spherical geometries

We investigate the effect of the hydrodynamic dispersion of the metal on various electromagnetic related surface effects in spherical geometries by calculating the general expression for the electromagnetic Green's function. The Green's function yields the multipolar polarizabilities for the metallic sphere and the dispersion relation for surface plasmons. The hydrodynamic dispersion is shown to lead to considerable shift of the surface-plasmon frequencies, which are pushed into the region in which they would not occur had the metal been characterized by the local dielectric function. The Green's function is further used to study the decay of an excited molecule near the metal surface and the molecular polarizability renormalizations. Various resonances in the decay characteristics of the excited molecule are shown to correspond to the shifted surface-plasmon frequencies.