Prompt electron emission characterization in UV laser ablation of metallic targets

We report on prompt emission of fast electrons occurring during nanosecond excimer laser ablation of metallic targets in vacuum. Prompt electrons yield and most probable kinetic energy as a function of the laser pulse fluence have been obtained by charge collection and time of flight techniques. The experimental data show a strong dependence of the prompt electrons yield on laser fluence. In particular, the data follow a power law dependence with two distinct slopes, below and above approximately ≈5 Jcm-2. Also the ion yield shows a similar behavior. The observed roll-off in the electron and ion dependence on the laser fluence has been discussed in terms of laser plasma shielding effects.