ELECTRON-IMPACT EXCITATION RATES OF NA-LIKE IONS

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 approximatio n. Eleven target terms are included in the expansion of the total wave -function. These collision strengths are averaged over a Maxwellian ve locity distribution to obtain effective collision strengths as a funct ion of electron temperature. The resulting values are compared with th e results of previous less elaborate calculations to find some disagre ements.