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 ve 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 eective colli-sion strengths as a function of electron temperature. The resulting values are compared with the results of previous less elaborate calculations to nd some disagreements. Key words: atomic data 1