R-matrix electron-impact excitation data for astrophysically abundant sulphur ions

Abstract

We present results for the electron-impact excitation of highly-charged sulphur ions (S8+ - S11+) obtained using the intermediate-coupling frame transformation R-matrix approach. A detailed comparison of the target structure has been made for the four ions to assess the uncertainty on collision strengths from the target structure. Effective collision strengths (\Upsilon s) are presented at temperatures ranging from 2\times10^2(z+1)^2 K to 2\times10^6(z+1)^2 K (where z is the residual charge of ions. Detailed comparisons for the \Upsilon are made with the results of previous calculations for these ions, which will pose insight on the uncertainty in their usage by astrophysical and fusion modelling codes.