Electron-excitation of the fine-structure transitions |

in Hydrogen-like ions He-II and Fe-XXVI |

Kisielius.R, Berrington.KA, Norrington.PH |

Astronomy & Astrophysics Supplement Series, 1996, Vol.118, No.1, pp.157-162 |

Electron excitation collision strengths for fine-structure transitions involving relativistic levels with principal quantum number n = 1, 2, 3, 4 in hydrogen-like ions He II and Fe XXVI are calculated using R-matrix techniques. The model target ion includes all 25 energy levels with n less than or equal to 5. Low-energy collision strengths dominated by autoionizing resonances are averaged over a Maxwellian velocity distribution to obtain effective collision strengths as a function of electron temperature. In the case of He II, such resonances enhance the collision strength by up to a factor of 3 over earlier calculations for excitation of the n = 4 levels due to the presence of 5ln'l' doubly-excited states near the n = 4 thresholds. For He II, the data are presented at four temperature points ranging from log T(K) = 3.2 to 4.3, and for Fe XXVI from log T(K) = 6.0 to 7.5.