Atomic data from the IRON Project LXV. Electron-impact excitation of Fe6+

M.C. Witthoeft, N.R. Badnell

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23 Citations (Scopus)

Abstract

We present R-matrix results for the electron-impact excitation of Fe6+. The intermediate-coupling frame transformation (ICFT) method has been used to obtain level-resolved collision strengths. We then calculate effective collision strengths assuming a Maxwellian distribution for the incident electron velocities. A large configuration interaction (CI) expansion of 1896 LS terms (4776 fine-structure levels) is used to obtain an accurate target. This is reduced to 89 close-coupling (CC) terms (189 levels) for the scattering calculation. To investigate the importance of CI, we also perform a second calculation with the same CC expansion but a smaller CI expansion. We discuss the difficulties of such a comparison and look at which transitions show the most sensitivity to the CI expansion. Our effective collision strengths are compared with a previous IRON Project report (Berrington et al. 2000, A&A, 142, 313) for transitions within the ground configuration and a recent distorted wave calculation (Zeng et al. 2005, MNRAS, 357, 440) for transitions to excited configurations. We find good agreement with the results of the previous R-matrix calculation and with the high-temperature distorted-wave results for most transitions, although there are some significant differences at lower temperatures in the latter case.
Original languageEnglish
Pages (from-to)543-551
Number of pages8
JournalAstronomy and Astrophysics
Volume481
Issue number2
DOIs
Publication statusPublished - Apr 2008

Keywords

  • atomic data
  • intermediate-coupling frame transformation
  • Maxwellian distribution
  • configuration interaction

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