|Electron-impact excitation of n = 3, 4 levels of Fe|
|M.C. Witthoeft, N.R. Badnell, G. del Zanna, K.A. Berrington and J.C. Pelan|
|Astronomy & Astrophysics, 2006, Vol.446, p 361|
We present results for electron-impact excitation of F-like Fe calculated using R-matrix theory where an intermediate-coupling frame transformation (ICFT) is used to obtain level-resolved collision strengths. Two such calculations are performed, the first expands the target using 2s 2p, 2s2p, 2s 2p 3l, 2s 2p 3l, and 2p 3l configurations while the second calculation includes the 2s 2p 4l, 2s 2p 4l, and 2p 4l configurations as well. The effect of the additional structure in the latter calculation on the n=3 resonances is explored and compared with previous calculations. We find strong resonant enhancement of the effective collision strengths to the 2s 2p 3s levels. A comparison with a Chandra X-ray observation of Capella shows that the n=4 R-matrix calculation leads to good agreement with observation.