Pulsed laser ablation of gold at 1 064 nm and 532 nm

A Nd:Yag laser, 9 ns pulse duration and 900 mJ maximum pulse energy, operating at the 1 064 nm fundamental wavelength and 532 nm second harmonic, is employed to irradiate Au targets placed in vacuum by using single laser pulses. The laser ablation is investigated in terms of ablation threshold, ablation yield, crater production and angular emission. The produced plasma emits ions at different charge state, from 1+ up to 6+, with supersonic velocity and kinetic energies up to about 3 keV, as demonstrated by time-of-flight measurements. The ion energy distributions vs. the charge state are obtained at the two wavelengths. The Boltzmann-Coulomb-shifted distributions depend regularly on the charge state, indicating the presence of a high electric field inside the non-equilibrium plasma. Measurements of plasma characterization, in terms of temperature, density and fractional ionization, are presented and discussed.