Electron Impact Excitation of S III: An Assessment

Abstract

In a recent paper, Tayal et al. (Astrophys. J. Suppl. 2019, 242, 9) reported results for energy levels, radiative rates (A-values), and effective collision strengths ( Υ ) for transitions among the 198 levels of Si-like S III. For the calculations, they adopted the multi-configuration Hartree–Fock (MCHF) code for the energy levels and A-values and the B-spline R-matrix (BSR) code for Υ . Their reported results appear to be accurate for energy levels and A-values, but not for Υ . Through our independent calculations by adopting the flexible atomic code (FAC), we demonstrate that their reported results for Υ are underestimated, by up to a factor of two, and at all temperatures, particularly for the allowed transitions, but some forbidden ones as well. Additionally, for transitions involving the higher levels, the behaviour of their Υ results is not correct.