L -shell photoionization of Mg-like S4+ in ground and metastable states: Experiment and theory

Abstract

We report measurements of the absolute photoionization cross sections of the magnesium-like S 4+ ion over the 160-270 eV photon energy range. The experiments were performed with the Multi-Analysis Ion Apparatus (MAIA) at the SOLEIL synchrotron radiation facility. Single and double ionization ion yields produced by the photoionization of the 2p subshell of the S 4+ ion both from the 2p 6 3s 2 1 S0 ground state and the 2p 5 3s3p 3 P0,1,2 metastable levels were observed, as well as 2s excitations. Calculations of the photoionization cross sections were carried out using Multi-Configuration Dirac-Fock and R-matrix codes and the results are compared with the experimental data.

L-Shell Photoionization of Magnesium-like Ions with New Results for Cl5+

“…In many cases, some of the thresholds of the target system are already known, and this information can be used to help in the R-matrix approach. This was indeed the case for S 4+ [18], but not for Cl 5+ . It is therefore interesting to see how the R-matrix code works for the latter when compared with the former.…”

“…For the recent analogous investigations of photoionization of S 4+ , we used two quite disparate theoretical approaches--MCDF and R-matrix theory [18]. We used the same methods to predict and interpret the new Cl 5+ results presented here.…”

“…In this article, we report the first study of L-shell photoionization of magnesium-like Cl 5+ for photon energies between 190 and 370 eV, straddling the 2s and 2p inner-shell excitation regimes. It is interesting to compare the success of the Multi-Configuration Dirac Fock (MCDF) and the R-matrix theoretical treatments of Cl 5+ with the success of the previous analogous treatments of S 4+ [18]. Our results provide experimental absolute photoionization cross sections for Cl 5+ , a comparison with the theoretical predictions of both the MCDF and the R-matrix approaches, as well as insights into the evolution along the isoelectronic sequence from Al + to Cl 5+ .…”

“…Photon-driven excitation and ionization along the magnesium isoelectronic sequence have long been of interest in experimental and theoretical investigations e.g., [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. This is not surprising, given the nature of magnesium-like systems with their simple closedsubshell ground state configuration 2p 6 3s 2 .…”

“…Absolute cross sections for L-shell (2s and 2p) photoionization along the magnesium series have been previously obtained through synchrotron radiation-based merged-beam experiments for Al + [9,31], Si 2+ [10], S 4+ [18], and Fe 14+ [32], with the latter produced in an electron beam ion trap. These experiments have been complemented by various theoretical investigations.…”