A quasi-molecular mechanism of formation of hydrogen in the early Universe -- a scheme of calculation

Abstract

In our recent papers (Kereslidze et all 2019a, 2021) a non-standard quasi-molecular mechanism was suggested and applied to treat the cosmological recombination. It was assumed that in the pre-recombination stage of evolution of the Universe an electron combined with two neighbouring protons and created the hydrogen molecular ion, $H_2^+$ in highly excited states, which then descended into the lower-lying states or dissociated. In this work, we elaborate the scheme of calculation for free-bound radiative transitions into attractive states of $H_2^+$ as functions of redshift $z$. Together with the earlier developed treatment of bound-bound radiative transitions in $H_2^+$, the elaborated scheme of calculation can be used for the design of a fast and complete cosmological recombination code.