Astronomy Letters

, Volume 31, Issue 6, pp 359–364

Recombination dynamics of primordial hydrogen and helium (He I) in the universe

  • V. K. Dubrovich
  • S. I. Grachev

DOI: 10.1134/1.1940107

Cite this article as:
Dubrovich, V.K. & Grachev, S.I. Astron. Lett. (2005) 31: 359. doi:10.1134/1.1940107


We calculated the ionization fraction for hydrogen and helium (He I) as a function of the redshift z by including the two-photon decays of high hydrogen and parahelium levels and the radiative transfer in the helium 23P1 ↔ 11S0 intercombination line. We show that this yields corrections of no more than a few percent to the ionization fraction for hydrogen and speeds up significantly the recombination for helium compared to the recent works by Seager et al. (1999, 2000), in which these effects were disregarded.

Key words

cosmology early Universe primordial helium recombination radio astronomy cosmic microwave background radiation 

Copyright information

© Pleiades Publishing, Inc. 2005

Authors and Affiliations

  • V. K. Dubrovich
    • 1
    • 2
  • S. I. Grachev
    • 3
  1. 1.Special Astrophysical Observatory, St. Petersburg BranchRussian Academy of SciencesSt. PetersburgRussia
  2. 2.Pulkovo Astronomical ObservatoryRussian Academy of SciencesSt. PetersburgRussia
  3. 3.Sobolev Astronomical InstituteSt. Petersburg State UniversitySt. PetersburgRussia

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