Electron impact excitation for He-like ions with Z = 20-42

Research output: Contribution to journalArticle


Aims. Spectral lines of He-like ions are among the most prominent features in X-ray spectra from a large variety of astrophysical and high-temperature fusion plasmas. A reliable plasma modeling and interpretation of the spectra require a large amount of accurate atomic data related to various physical processes. In this paper, we focus on the electron-impact excitation (EIE) process. Methods. We adopted the independent process and isolated resonances approximation using distorted waves (IPIRDW). Resonant stabilizing transitions and decays to lower-lying autoionizing levels from the resonances are included as radiative damping. To verify the applicability of the IPIRDW approximation, an independent Dirac R-matrix calculation was also performed. The two sets of results show excellent agreement. Results. We report electron impact excitation collision strengths for transitions among the lowest 49 levels of the 1snl(n ≤ 5; l ≤ (n - 1)) configurations in He-like ions with 20 ≤ Z ≤ 42. The line ratios R and G are calculated for Fe XXV and Kr XXXV. Conclusions. Compared to previous theoretical calculations, our IPIRDWcalculation treats resonance excitation and radiative damping effects more comprehensively, and the resulting line emission cross sections show good agreement with the experimental observations. Our results should facilitate the modeling and diagnostics of various astrophysical and laboratory plasmas.


  • R. Si
  • S. Li
  • K. Wang
  • X. L. Guo
  • Z. B. Chen
  • J. Yan
  • C. Y. Chen
  • T. Brage
  • Y. M. Zou
External organisations
  • Fudan University
  • Institute of Applied Physics and Computational Mathematics (IAPCM), Beijing
  • Hebei University
  • National University of Defense Technology
  • Second Military Medical University
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Atom and Molecular Physics and Optics


  • Atomic data, Atomic processes
Original languageEnglish
Article numberA85
JournalAstronomy and Astrophysics
Publication statusPublished - 2017 Apr 1
Publication categoryResearch