Electron-impact study ofS3using theR-matrix method

Abstract

We have carried out a comprehensive study of electron impact on the open-chain ${\mathrm{S}}_{3}$ isomer by using the $R$-matrix method. Elastic (integrated and differential), momentum-transfer, excitation, and ionization cross sections, along with effective collision frequency over a wide electron temperature range (500--30 000 K) have been presented. The target states are represented by including correlations via a configuration interaction technique. The results of the static-exchange, correlated 1-state, and 24-state close-coupling approximations are presented. Our study has detected a shape resonance, six core-excited shape resonances, and one Feshbach resonance in the $24$-state model. We detect a stable bound state of ${\mathrm{S}}_{3}^{\ensuremath{-}}$ of ${}^{2}{B}_{1}$ symmetry having a configuration $\dots{}11{a}_{1}^{2},\dots{}3{b}_{1}^{2}4{b}_{1},\dots{}8{b}_{2}^{2},\dots{}2{a}_{2}^{2}$, with a vertical electronic affinity value of 2.15 eV, and a ionization potential value of 9.77 eV, which are in good agreement with the experimental values of $2.093\ifmmode\pm\else\textpm\fi{}0.025$ and $9.68\ifmmode\pm\else\textpm\fi{}0.03$ eV, respectively. The ionization cross sections are calculated using the binary-encounter-Bethe model in which Hartree-Fock molecular orbitals at a self-consistent level are used to calculate kinetic and binding energies of the occupied molecular orbitals. We have used partial waves up to $l=4$ to represent continuum electron in our $R$-matrix method. A Born top-up procedure is invoked to account for the contribution of partial waves higher than $l=4$ to obtain converged cross sections.