Impact of a quasi-molecular mechanism of cosmological recombination on the population of the 2s-level of hydrogen

The recombination epoch is one of the most important stages of the evolution of the universe. Around 4X105 years after the Big Bang, the temperature of the Universe dropped significantly. This allowed for the electron and a proton to form a bound system, a neutral hydrogen atom. According to the standard mechanism of cosmological recombination, the electron emits a photon and creates a hydrogen atom in a highly excited state. Afterward, the electron cascades to the ground state. According to the calculations, at the pre-recombination stage of the early Universe, when the temperature was higher than subsequently, the distance between protons was comparable to the linear size of the hydrogen atom in a highly excited state. This means that the nearest neighboring proton participated in the process and thus had an influence on recombination. The main goal of this work is to study how important is the influence of the second proton on the formation of atomic hydrogen and, accordingly, to determine the impact of the quasi-molecular mechanism of recombination on the evolution of the Universe.