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arXiv · 2203.06575

Revisiting the quasi-molecular mechanism of recombination

Zhiqi Huang
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Abstract

The quasi-molecular mechanism of recombination, recently suggested by Kereselidze et al., is a non-standard process where an electron and two neighboring protons in the early universe directly form an ionized hydrogen molecule in a highly excited state, which then descends to lower levels or dissociates. It has been suggested that the increased binding energy due to the participation of a second proton may lead to an earlier cosmic recombination that alleviates the Hubble tension. Revisiting the quasi-molecular channel of recombination in more details, we find that the original work significantly overestimated the probability of finding a pair of adjacent protons in the relevant epoch ($z\sim $ a few thousand). Our new estimation suggests that the quasi-molecular mechanism of recombination cannot be the primary cause of the Hubble tension.

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Zhiqi Huang. 2022-03-13. Revisiting the quasi-molecular mechanism of recombination. https://doi.org/10.1093/mnras/stac1127

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