Collision strengths and rate coefficients for excitation of He-like ions by electron impact

摘要

We present collision strengths and rate coefficients for electron-impact excitation of He-like ions (S~(14+), Ar~(16+), Ca~(18+)) using the Dirac Atomic R-matrix Code, which has been developed by Norrington and Grant [J. Phys. B: At. Mol. Opt. Phys. 20 (1987) 4869]. The lowest 45 target levels are included in the calculation to obtain the rate coefficients for the 1s~2 ~1S_0-1snl ~(1,3)L_J (n = 2,3,4; l= 0,1,2,3). Results are compared with those available in previous calculations.