On the validity of the ICFT R-matrix method : Fe xiv

Del Zanna, G. and Badnell, N. R. and Fernandez-Menchero, L. and Liang, G. Y. and Mason, H. E. and Storey, P. J. (2015) On the validity of the ICFT R-matrix method : Fe xiv. Monthly Notices of the Royal Astronomical Society, 454. pp. 2909-2917. ISSN 0035-8711 (https://doi.org/10.1093/mnras/stv2016)

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Recently, Aggarwal & Keenan published a Dirac R-matrix (darc) calculation for the electron-impact excitation of Fe xiv. A 136-level configuration-interaction/close-coupling (CI/CC) expansion was adopted. Comparisons with earlier calculations, obtained by Liang et al. with the intermediate coupling frame transformation (ICFT) R-matrix method, showed significant discrepancies. One of the main differences was that the Liang et al. effective collision strengths were consistently larger. Aggarwal & Keenan suggested various possible causes for the differences. We discuss them in detail here. We have carried out an ICFT R-matrix calculation with the same 136-level CI/CC expansion adopted by Aggarwal & Keenan, and compared the results with theirs and with those of Liang et al., which employed a much larger CI/CC expansion. We find that the main differences arise because of the different CC and CI expansions, and not because of the use of the ICFT method, as suggested by Aggarwal & Keenan. The significant increase in the effective collision strengths obtained by Liang et al. is mainly due to the extra resonances that are present because of the larger target expansion.


Del Zanna, G., Badnell, N. R. ORCID logoORCID: https://orcid.org/0000-0001-7418-7996, Fernandez-Menchero, L., Liang, G. Y., Mason, H. E. and Storey, P. J.;