Electron-impact excitation of FeII - Collision strengths and effective collision strengths for low-lying fine-structure forbidden transitions

C. A. Ramsbottom*, C. E. Hudson, P. H. Norrington, M. P. Scott, Catherine Ramsbottom

*Corresponding author for this work

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

Context. Absorption or emission lines of Fe II are observed in many astrophysical spectra and accurate atomic data are required to interpret these lines. The calculation of electron-impact excitation rates for transitions among even the lowest lying levels of Fe II is a formidable task for theoreticians.

Aims. In this paper, we present collision strengths and effective collision strengths for electron-impact excitation of Fe II for low-lying forbidden transitions among the lowest 16 fine-structure levels arising from the four LS states 3d(6)4s D-6(e), 3d(7) F-4(e), 3d(6)4s D-4(e), and 3d(7) P-4(e). The effective collision strengths are calculated for a wide range of electron temperatures of astrophysical importance from 30-100 000 K.

Methods. The parallel suite of Breit-Pauli codes are utilised to compute the collision cross sections for electron-impact excitation of Fe II and relativistic terms are included explicitly in both the target and the scattering approximation. 100 LS or 262-jj levels formed from the basis configurations 3d(6)4s, 3d(7), and 3d(6)4p were included in the wavefunction representation of the target, including all doublet, quartet, and sextet terms. Collision strengths for a total of 34191 individual transitions were computed.

Results. A detailed comparison is made with previous theoretical works and significant differences were found to occur in the effective collision strengths, particularly at low temperatures.

Original languageEnglish
Pages (from-to)765-769
Number of pages5
JournalAstronomy and Astrophysics
Volume475
Issue number2
DOIs
Publication statusPublished - Nov 2007

Keywords

  • atomic data
  • atomic processes
  • plasmas
  • R-MATRIX METHOD
  • ATOMIC DATA
  • EMISSION-LINES
  • IRON-PROJECT
  • SPECTRA
  • PROGRAM
  • STATE

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