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

1 June 2005

journal article
Published by Pleiades Publishing Ltd in Astronomy Letters

Vol. 31 (6) , 359-364
https://doi.org/10.1134/1.1940107

Abstract

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 ↔ 1¹ S ₀ 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.

Keywords

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