Influence of lattice contraction on the optical properties and the electron dynamics in silver clusters
Résumé
The effects of surface-induced lattice contraction on the size evolution of the surface plasmon resonance and of the electronic thermalization time in small silver clusters have been investigated in the framework of a mixed classical/quantum model. The increase of the conduction-electron density results in a blue-shift trend for decreasing cluster size. However this effect is counterbalanced by the increase of the dielectric function associated to the ionic-core background. Agreement with the blue-shift trend observed in experiment is recovered by introducing an inner surface skin of vanishing ionic-core polarizability having a thickness practically unchanged as compared to previous estimations. The influence of the lattice contraction on the electron dynamics is also discussed. It is shown that this influence is negligible as compared to the surface effects arising from the spillout and the inner skin of reduced ionic-core polarizability which are both responsible for a decrease of the electron thermalization time as the particle size decreases.