ATOMIC DATA FROM THE IRON PROJECT .15. 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-m atrix techniques. The model target ion includes all 25 energy levels w ith n less than or equal to 5. Low-energy collision strengths dominate d by autoionizing resonances are averaged over a Maxwellian velocity d istribution to obtain effective collision strengths as a function of e lectron temperature. In the case of He Ir, such resonances enhance the collision strength by up to a factor of 3 over earlier calculations f or 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 pre sented 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.