Abstract
Electron-impact excitation collision strengths of the Fe-peak element Fe IV are calculated in the close-coupling approximation using the R-matrix suite of codes PRMAT designed for parallel processors. One hundred and eight LS-coupled states arising from the 3d5, 3d44s and 3d44p configurations of Fe IV, are retained in the present calculations. Detailed multi-configuration interaction target wavefunctions are used with the aid of 3p2 → 3d2 electron promotions and a correlation orbital in the present calculations. Effective collision strengths for optically forbidden transitions, which are extremely important in the analysis of lines in the Fe IV spectra, are obtained by averaging the electron collision strengths for a wide range of incident electron energies, over a Maxwellian distribution of velocities. Results are presented for electron temperatures (Te in Kelvin) in the range 3.3 ⩽ Log Te⩽ 6.0 applicable to many laboratory and astrophysical plasmas for transitions within the 3d5 manifold. The present results compared to previous investigations provide improved results for important lines in the Fe IV spectrum.
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