Ultrafast electron dynamics in metal nanoparticles: decay times of surface plasmon excitation

Summary form only given. We present results obtained by a recently developed technique to determine the homogeneous linewidths of surface plasmon resonances of metal nanoparticles and thus measure T/sub 2/. The method is based on spectral hole burning in the inhomogeneously broadened absorption profiles of metal nanoparticles and has been applied to supported oblate Ag clusters with radii of only few nanometers. From the experimental results and a theoretical model of hole burning, decay times of as little as 3.5 fs have been obtained. This value is shorter than expected for damping by bulk electron scattering. We conclude that additional damping mechanisms, in particular surface scattering, come into play if the electrons are confined in particles with sizes below 10 nm. Furthermore, an influence of the shape of the clusters on the decay time was observed.