Resolution of the forbidden (J = 0 → 0) excitation puzzle in Mg-like ions

Fernández-Menchero, L. and Del Zanna, G. and Badnell, N. R. (2015) Resolution of the forbidden (J = 0 → 0) excitation puzzle in Mg-like ions. Astronomy and Astrophysics, 577. A95. ISSN 0004-6361 (https://doi.org/10.1051/0004-6361/201525711)

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Abstract

We investigate the source of the discrepancy between R-matrix and distorted-wave (DW) collision strengths for J − J′ = 0–0 transitions in Mg-like ions, for example 3s21S0–3p21S0, as reported previously. We find it to be due to the neglect of coupling, for example via 3s3p 1P1, as done by most DW codes. We have implemented an option to account for such coupling as a perturbation within the autostructure DW code. This removes the discrepancy of a factor ~10 and ~100 for Fe14 + and S4 +, respectively, for such transitions. The neglect of coupling would have affected (to some degree) the atomic data for a few weak optically forbidden transitions in other isoelectronic sequences if they were calculated with DW codes such as FAC and HULLAC. In addition, we compare the Fe14 + line intensities predicted with the R-matrix collision strengths against observations of solar active regions and flares; they agree well. For Fe14 +, we suggest that the best density diagnostic ratio is 327.0/321.8 Å.

ORCID iDs

Fernández-Menchero, L., Del Zanna, G. and Badnell, N. R. ORCID logoORCID: https://orcid.org/0000-0001-7418-7996;
  • Item type:Article
    ID code:53093
    Dates:
    Date
    Event
    May 2015
    Published
    8 May 2015
    Published Online
    8 April 2015
    Accepted
    Subjects:Science > Physics
    Department:Faculty of Science > Physics
    Depositing user: Pure Administrator
    Date deposited:26 May 2015 13:03
    Last modified:11 Nov 2024 11:05
    Related URLs:
    URI:https://strathprints.strath.ac.uk/id/eprint/53093
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