Electron-impact excitation of FeII

We have applied the $B$-spline $R$-matrix method~[1,2] to study electron-impact excitation of Fe$^+$ over an energy range from threshold to 5$\,$eV. A major challenge for this astrophysically important collision system is the very complex target structure, with a strong term-dependence in the individual orbitals. Using a multi-configuration Hartree-Fock method with non-orthogonal orbitals allows us to generate individually optimized term-dependent orbitals and thereby limit the number of configurations that need to be kept in both the $N$-electron target and the $(N+1)$- electron collision problems. Overall, our results for individual cross sections and effective collision strengths are in qualitative agreement with the predictions by Ramsbottom {\it et al.}~[3], but we find significant discrepancies in the very complex near-threshold resonance structure. \par\noindent [1] O. Zatsarinny and C. Froese Fischer, J. Phys. B~{\bf 33}, 313 (2000). \par\noindent [2] O. Zatsarinny and K. Bartschat, J. Phys. B~{\bf 37}, 2173 (2004). \par\noindent [3] C.A. Ramsbottom, C.J. Noble, V.M. Burke, M.P. Scott and P.G. Burke, J. Phys. B~{\bf 37}, 3609 (2004).