Space- and time-resolved optical diagnosis for the study of laser ablation plasma dynamics

The dynamics of transient plasmas generated by high-fluence nanosecond laser ablation has been investigated by means of optical methods (time- and space-resolved emission spectroscopy and fast ICCD imaging). Systematic measurements have been carried out on plasma produced in vacuum (10−8 Torr residual pressure) by Nd:YAG laser (10 ns, 532 nm) irradiation of Aluminum targets. Al neutral atoms and different charge state ions have been monitored through the evolution of corresponding spectral lines. The study evidenced the presence of two different groups of particles, tentatively related to two distinct ejection mechanisms. This behavior has been confirmed by the fast ICCD (20 ns gate) recording of the total optical emission of the plume. The application of the relative line intensity method to the study of the excitation temperature axial profile is equally discussed.