Three-body recombination of hydrogen in the early Universe

Abstract

ABSTRACT It has been suggested recently that three-body recombination of two protons and an electron might be significant in the formation of atomic hydrogen in the early Universe. We demonstrate that this process is completely negligible in the primordial plasma and that the value of the redshift, at which the transition from ionized to atomic hydrogen occurs, is determined by an equilibrium between the rates of two-body radiative recombination of a proton and an electron and its inverse, namely photoionization of atomic hydrogen.