Characterization of fast electron emission in UV laser ablation of metallic targets

We report on prompt emission of fast electrons occurring during nanosecond excimer laser ablation of aluminum targets in vacuum. We have measured both the kinetic energy distribution and the energy-integrated time-of-flight distribution of these electrons, in the fluence range 1-10 Jcm(-2). Moreover, at higher laser fluences, the yield of prompt electrons and the most probable kinetic energy as a function of the laser pulse fluence have also been obtained by charge collection and time-of-flight measurements. The experimental data show that the prompt electrons are produced during the laser pulse as a consequence of two-photon processes, and that space-charge effects influence the photoemitted electron kinetic energy leading to prompt electrons with most probable kinetic energies up to approximate to 15 eV, in the investigated fluence range.