Photoionization of the Ne-likeSi4+ion in ground and metastable states in the 110–184-eV photon energy range

Abstract

We present measurements of the absolute photoionization cross section of the neonlike ${\text{Si}}^{4+}$ ion over the 110--184 eV photon energy range. The measurements were performed using two independent merged-beam setups at the super-ACO and ASTRID synchrotron-radiation facilities, respectively. Signals produced in the photoionization of the $2p$ subshell of the ${\text{Si}}^{4+}$ ion both from the $2{p}^{6}\text{ }{^{1}S}_{0}$ ground state and the $2{p}^{5}3s\text{ }{^{3}P}_{0,2}$ metastable levels were observed. Calculations of the $2p$ photoionization cross sections were carried out using a multi-configuration Dirac-Fock code. They give results in good agreement with the measured spectra. Comparison with other available theoretical results is also presented.