Atomic data from the IRON Project. XV. Electron excitation of the fine-structure transitions in hydrogen-like ions He II and Fe XXVI.
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<=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 logT(K)=3.2 to 4.3, and for Fe XXVI from logT(K)=6.0 to 7.5.
Astronomy and Astrophysics Supplement Series
- Pub Date:
- July 1996
- ATOMIC DATA