Electron Impact Excitation of S III: an Assessment

Abstract

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