Oscillatory size dependence of the surface plasmon linewidth in metallic nanoparticles

We study the linewidth of the surface plasmon resonance in the optical absorption spectrum of metallic nanoparticles, when the decay into electron-hole pairs is the dominant channel. Within a semiclassical approach, we find that the electron-hole density-density correlation oscillates as a function of the size of the particles, leading to oscillations of the linewidth. This result is confirmed numerically for alkali and noble-metal particles. While the linewidth can increase strongly, the oscillations persist when the particles are embedded in a matrix.