  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.
