Paper LX

Electron-impact excitation of n = 3, 4 levels of Fe$^{17+}$

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$^2$ 2p$^5$, 2s2p$^6$, 2s$^2$ 2p$^4$ 3l, 2s 2p$^5$ 3l, and 2p$^6$ 3l configurations while the second calculation includes the 2s$^2$ 2p$^4$ 4l, 2s 2p$^5$ 4l, and 2p$^6$ 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$^2$ 2p$^4$ 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.