Theoretical study for photoionization of Mg-like S4+ ion

Photoionization of the Mg-like S4+ ion has been studied for the ground S-1 and excited P-3,P-1 initial states. Using a noniterative eigenchannel R-matrix method, we have investigated the partial photoionization cross sections leading to the final photo-ionic 3l states. The autoionizing resonance structures arising from the ground and excited states are identified and characterized. Our calculational results, which show excellent agreement between length and velocity gauges, are compared with the available previous Opacity Project results, and some significant discrepancies are found.