Electron-impact excitation of Fe2+ : a comparison of intermediate coupling frame transformation, Breit-Pauli and Dirac R-matrix calculations

Badnell, N. R. and Ballance, C. P. (2014) Electron-impact excitation of Fe2+ : a comparison of intermediate coupling frame transformation, Breit-Pauli and Dirac R-matrix calculations. Astrophysical Journal, 785 (2). ISSN 0004-637X

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    Abstract

    Modeling the spectral emission of low-charge iron group ions enables the diagnostic determination of the local physical conditions of many cool plasma environments such as those found in H II regions, planetary nebulae, active galactic nuclei, etc. Electron-impact excitation drives the population of the emitting levels and, hence, their emissivities. By carrying-out Breit-Pauli and intermediate coupling frame transformation (ICFT) R-matrix calculations for the electron-impact excitation of Fe2 +, which both use the exact same atomic structure and the same close-coupling expansion, we demonstrate the validity of the application of the powerful ICFT method to low-charge iron group ions. This is in contradiction to the finding of Bautista et al., who carried-out ICFT and Dirac R-matrix calculations for the same ion. We discuss possible reasons.