Analysis of the xuv photoabsorption spectrum ofAu2+,Au3+, andAu4+

Abstract

The photoabsorption processes of ${\text{Au}}^{2+}$, ${\text{Au}}^{3+}$, and ${\text{Au}}^{4+}$ have been investigated experimentally and theoretically in the 70--127 eV region. Using the dual laser-produced plasma technique, the $4f$ and $5p$ photoabsorption spectrum has been recorded at 50 ns time delay and was found to be dominated by a great number of lines from $4f\text{\ensuremath{-}}5d$, $6d$ and $5p\text{\ensuremath{-}}5d$, $6s$ transitions, which have been identified by comparison with the aid of Hartree-Fock with configuration interaction calculations. The characteristic feature of the spectrum is that satellite lines from excited configurations containing one or two $6s$ electrons are more important than resonance lines, and with increasing ionization, satellite contributions from states with one $6s$ spectator electron gradually become more important than those with two $6s$ spectator electrons. Based on the assumption of a normalized Boltzmann distribution among the excited states and a steady-state collisional-radiative model, we succeeded in reproducing a spectrum which is in good agreement with experiment.