Optical diagnostics of gold plasmas produced by infrared laser ablation

Laser plasmas produced by ablation of a gold target in a vacuum are spatially and temporally characterized by optical emission spectroscopy. A Nd:YAG laser (1064 nm, pulse width 15 ns and fluences of 5.8 and 11 J/cm(2)) is used to ablate the Au target. Au, Au+ and Au2+. species were studied both as a function of the location from the target surface and of the time delay from the laser pulse arrival. Plasma temperature, electron density and average velocities were measured from the spatiotemporal analysis. The results show a faster decay of the continuum emission, Au2+ and Au+ species than in the case of neutral Au atoms. Higher velocities and a narrower temporal distribution of Au+ ions are observed when compared to Au atoms. Electron temperature was evaluated from the comparison of Au atomic-Boltzmann local thermodynamic equilibrium spectra with experimental ones at various delay times from the laser pulse incidence. Electron densities and electron temperatures approximately decrease from 2.3 to 1.1 x 10(18) cm(-3) and from 1.6 to 0.4 eV, respectively, as the delay time increases along the first 2 mu s of plasma evolution. (C) 2020 Elsevier Ltd. All rights reserved.