Electron-impact excitation rates of Na-like ions

Abstract

Electron excitation collision strengths for all the transitions among 3s, 3p, 3d, 4s, 4p, 4d, 4f states of the five Na-like ions Al III, Si IV, S VI, Ar VIII and Ca X are calculated in the R-matrix approximation. Eleven target terms are included in the expansion of the total wave-function. These collision strengths are averaged over a Maxwellian velocity distribution to obtain effective collision strengths as a function of electron temperature. The resulting values are compared with the results of previous less elaborate calculations to find some disagreements.