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

摘要

We present Maxwellian-averaged effective collision strengths for theelectron-impact excitation of S III over a wide range of electron temperaturesof astrophysical importance, log T(K) = 3.0-6.0. The calculation incorporates53 fine-structure levels arising from the six lowest configurations, givingrise to 1378 individual lines, and is undertaken using the recently developedRMATRX II plus FINE95 suite of codes. A detailed comparison is made with aprevious R-matrix calculation and significant differences are found for sometransitions. The atomic data are subsequently incorporated into the modelingcode CLOUDY to generate line intensities for a range of plasma parameters, withemphasis on allowed UV and EUV emission lines detected from the Io plasmatorus. Electron density-sensitive line ratios are calculated with the presentatomic data and compared with those from CHIANTI v7.1, as well as with Ioplasma torus spectra obtained by FUSE and EUVE. The present line intensitiesare found to agree well with the observational results and provide a noticeableimprovement upon the values predicted by CHIANTI.