Theory for nonlinear Mie-scattering from spherical metal clusters

Using classical electrodynamics we determine the angular dependence of the light intensities radiated in second and third harmonic generation by spherical metal clusters. Forward and backward scattering is analyzed in detail. Also resonance effects in the integrated intensities are studied. By treating intermediate cluster sizes, we complete the scattering theory for spherical clusters between Rayleigh-type analysis for small spheres and geometrical optics for spheres much larger than the wavelength for nonlinear optics. The particle size sensitivity of Mie-scattering is increased by nonlinearity. The results suggest that small particle sizes can be extracted more easily from nonlinear optics.