Size effects in the ultrafast electronic dynamics of metallic tin nanoparticles

We report on femtosecond transient reflectivity measurements performed on metallic tin nanoparticles, embedded in an ${\mathrm{Al}}_2$ ${\mathrm{O}}_3$ matrix, with average radii in the range 20–60 Å. It was observed that the time behavior of the transient reflectivity decays depends upon particle size. The results can be interpreted in terms of a size-dependent electron-surface interaction in the thermalization process and of a substantially size-independent electron-electron thermalization. © 1996 The American Physical Society.