Fine structure effective collision strengths for the electron impact excitation of S V

School of Mathematics and Physics, The Queens University of Belfast, Belfast BT7 1NN, Northern Ireland, UK e-mail: c.hudson@am.qub.ac.uk

Received: 21 December 2005
Accepted: 15 February 2006

Abstract

Context. emission lines have been observed in solar flares, solar upper atmospheres, quiet sun regions and broad band absorption line quasars, with particular lines being used as diagnostics for electron temperature and density. Accurate atomic data are needed to analyse the observational data and to date the best available calculations for this ion have not included contributions from resonances.

Aims.To calculate fine structure effective collision strengths for the electron impact excitation of using a method which incorporates resonances.

Methods.A 14-state R-matrix calculation has been performed. The target states are represented by configuration interaction wavefunctions and consist of the 14 lowest LS states, having configurations (2p⁶)3s², 3s3p, 3p², 3s3d, 3s4s, 3p3d. These target states give rise to 26 fine structure levels and 325 possible transitions. The fine structure collision strengths were obtained by transforming to a jj-coupling scheme using the JAJOM program of Saraph and have been determined at a sufficiently fine energy mesh to delineate properly the resonance structure. The effective collision strengths were calculated by averaging the electron collision strengths over a Maxwellian distribution of velocities.

Results.Tabulations of the non-zero effective collision strengths for transitions between both the LS states and the fine structure levels are given for electron temperatures (T_e) in the range . Comparisons are made with previous R-matrix and distorted-wave calculations.