Testing atomic collision theory with the two-photon continuum of astrophysical nebulae

F. Guzmán, N. R. Badnell, M. Chatzikos, P. A.M. Van Hoof, R. J.R. Williams, G. J. Ferland

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Accurate rates for energy-degenerate l-changing collisions are needed to determine cosmological abundances and recombination. There are now several competing theories for the treatment of this process, and it is not possible to test these experimentally. We show that the H I two-photon continuum produced by astrophysical nebulae is strongly affected by lchanging collisions. We perform an analysis of the different underlying atomic processes and simulate the recombination and two-photon spectrum of a nebula containing H and He. We provide an extended set of effective recombination coefficients and updated l-changing 2s − 2p transition rates using several competing theories. In principle, accurate astronomical observations could determine which theory is correct.

Original languageEnglish
Pages (from-to)3944-3950
Number of pages7
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Jun 1 2017

Bibliographical note

Publisher Copyright:
© 2017 The Authors.


  • Atomic data
  • Atomic processes
  • Cosmic background radiation
  • Cosmology: observations
  • H II regions
  • Planetary nebulae: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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