Validity of the ICFT R-matrix method: Be-like Al 9+ a case study

L. Fernández-Menchero, G. Del Zanna, Nigel Badnell

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

We have carried out 98-level configuration-interaction/close-coupling (CI/CC) intermediate coupling frame transformation (ICFT) and Breit–Pauli R-matrix calculations for the electron-impact excitation of Be-like Al 9+. The close agreement that we find between the two sets of effective collision strengths demonstrates the continued robustness of the ICFT method. On the other hand, a comparison of this data with previous 238-level CI/CC ICFT effective collision strengths shows that the results for excitation up to n = 4 levels are systematically and increasingly underestimated over a wide range of temperatures by R-matrix calculations whose CC expansion extends only to n = 4 (98-levels). Thus, we find to be false a recent conjecture that the ICFT approach may not be completely robust. The conjecture was based upon a comparison of 98-level CI/CC Dirac R-matrix effective collision strengths for Al 9+ with those from the 238-level CI/CC ICFT R-matrix calculations. The disagreement found recently is due to a lack of convergence of the CC expansion in the 98-level CI/CC Dirac work. The earlier 238-level CI/CC ICFT work has a superior target to the 98-level CI/CC Dirac one and provides more accurate atomic data. Similar considerations need to be made for other Be-like ions and for other sequences.
LanguageEnglish
Pages4174-4183
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Volume450
Issue number4
Early online date20 May 2015
DOIs
Publication statusPublished - 11 Jul 2015

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matrix methods
matrix
configuration interaction
collision
method
collisions
electron
ion
expansion
calculation
electron impact
excitation
temperature
comparison

Keywords

  • atomic data
  • corona
  • intermediate coupling frame transformation

Cite this

Fernández-Menchero, L. ; Del Zanna, G. ; Badnell, Nigel. / Validity of the ICFT R-matrix method : Be-like Al 9+ a case study . In: Monthly Notices of the Royal Astronomical Society. 2015 ; Vol. 450, No. 4. pp. 4174-4183.
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Validity of the ICFT R-matrix method : Be-like Al 9+ a case study . / Fernández-Menchero, L.; Del Zanna, G.; Badnell, Nigel.

In: Monthly Notices of the Royal Astronomical Society, Vol. 450, No. 4, 11.07.2015, p. 4174-4183.

Research output: Contribution to journalArticle

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AU - Fernández-Menchero, L.

AU - Del Zanna, G.

AU - Badnell, Nigel

N1 - This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record Fernández-Menchero, L., Del Zanna, G., & Badnell, N. (2015). Validity of the ICFT R-matrix method: Be-like Al 9+ a case study . Monthly Notices of the Royal Astronomical Society, 450(4), 4174-4183. is available online at: http://mnras.oxfordjournals.org/content/450/4/4174.abstract

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N2 - We have carried out 98-level configuration-interaction/close-coupling (CI/CC) intermediate coupling frame transformation (ICFT) and Breit–Pauli R-matrix calculations for the electron-impact excitation of Be-like Al 9+. The close agreement that we find between the two sets of effective collision strengths demonstrates the continued robustness of the ICFT method. On the other hand, a comparison of this data with previous 238-level CI/CC ICFT effective collision strengths shows that the results for excitation up to n = 4 levels are systematically and increasingly underestimated over a wide range of temperatures by R-matrix calculations whose CC expansion extends only to n = 4 (98-levels). Thus, we find to be false a recent conjecture that the ICFT approach may not be completely robust. The conjecture was based upon a comparison of 98-level CI/CC Dirac R-matrix effective collision strengths for Al 9+ with those from the 238-level CI/CC ICFT R-matrix calculations. The disagreement found recently is due to a lack of convergence of the CC expansion in the 98-level CI/CC Dirac work. The earlier 238-level CI/CC ICFT work has a superior target to the 98-level CI/CC Dirac one and provides more accurate atomic data. Similar considerations need to be made for other Be-like ions and for other sequences.

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