Size-dependent electron-electron interactions in metal nanoparticles

The internal thermalization dynamics of the conduction electrons is investi gated in silver nanoparticles with radius ranging from 13 to 1.6 nm using a femtosecond IR pump-UV probe absorption saturation technique. A sharp incr ease of the electron energy exchange rate is demonstrated for nanoparticles smaller than 5 nm. The results are consistent with electron-electron scatt ering acceleration due to surface induced reduction of the Coulomb interact ion screening by the conduction and corp electrons.