Optical properties of small metal spheres

This is the authors' abstract. We don't add key points for this paper.

The classical Mie theory for the scattering and absorption of electromagnetic radiation by a sphere is extended so as to be applicable to cases in which longitudinal polarization waves can propagate in the sphere material. The extended Mie theory is applied to the calculation of the optical properties of small metal spheres, the electronic properties of which are represented by Boltzmann-type dielectric functions. It is found that the main plasma resonance is shifted from its classical position towards the high-frequency side, and that a secondary absorption structure appears just above the plasma frequency. The dependence of these effects on the physical parameters characterizing the sphere and its surroundings is investigated.