Oscillatory behavior and enhancement of the surface plasmon linewidth in embedded noble metal nanoparticles

We study the Landau damping of the surface plasmonresonance of metallic nanoparticles embedded in differentenvironments of experimental relevance. Important oscillationsof the plasmon linewidth as a function of the radius of thenanoparticles are obtained from numerical calculations based onthe time dependent local density approximation. Thesesize-oscillations are understood, within a semiclassicalapproximation, as a consequence of correlations in the spectraldensity of the nanoparticles. We treat inert matrices, as wellas the case with an unoccupied conduction band. In the lattercase, the plasmon lifetime is greatly reduced with respect tothe inert case, but the non-monotonous size-dependence persists.