Electron-Impact Excitation Collision Strengths and Theoretical Line Intensities for Fine-Structure Transitions in S III

TL;DR

This paper calculates detailed electron-impact excitation data for S III ions, improving the accuracy of plasma emission models and line intensity predictions relevant to astrophysical observations.

Contribution

It provides new Maxwellian-averaged collision strengths for S III with extensive fine-structure levels, using advanced R-matrix calculations, and integrates these into plasma modeling for better spectral predictions.

Findings

Significant differences found compared to previous calculations.

Improved agreement with observational spectra of Io plasma torus.

Enhanced line intensity predictions over existing databases.

Abstract

We present Maxwellian-averaged effective collision strengths for the electron-impact excitation of S III over a wide range of electron temperatures of astrophysical importance, log T(K) = 3.0-6.0. The calculation incorporates 53 fine-structure levels arising from the six lowest configurations, giving rise to 1378 individual lines, and is undertaken using the recently developed RMATRX II plus FINE95 suite of codes. A detailed comparison is made with a previous R-matrix calculation and significant differences are found for some transitions. The atomic data are subsequently incorporated into the modeling code CLOUDY to generate line intensities for a range of plasma parameters, with emphasis on allowed UV and EUV emission lines detected from the Io plasma torus. Electron density-sensitive line ratios are calculated with the present atomic data and compared with those from CHIANTI v7.1, as well as with Io plasma torus spectra obtained by FUSE and EUVE. The present line intensities are found to agree well with the observational results and provide a noticeable improvement upon the values predicted by CHIANTI.