Experimental confirmation of barrierless reactions between HeH<sup>+</sup> and deuterium atoms suggests a lower abundance of the first molecules at very high redshifts
The HeH + ion was the first molecule to form in the early Universe, and its comparatively large dipole moment renders it a potential coolant, relevant during the epoch of first star formation. The main destruction mechanisms under primordial conditions are recombination with free electrons and chemical reactions with hydrogen atoms. The latter process was believed to be slow at low temperatures, owing to a barrier forming along the reaction coordinate. Here we present a joint experimental and theoretical study of the reaction HeH + + D → HD + + He that confirms the very recent proposition that the reaction is, in fact, barrierless and fast at low collision energies. The present evidence suggests that previous studies underestimated the low-temperature rate coefficient significantly because of an artifact in a widely used potential energy surface, and calls for a reassessment of the helium chemistry in the early Universe.
Authors
- Yohann Scribano (ORCID: https://orcid.org/0000-0003-3875-5970)
- Xavier Urbain (ORCID: https://orcid.org/0000-0003-3326-8823)
- Florian Grussie (ORCID: https://orcid.org/0000-0002-1553-3622)
- Duncan Bossion (ORCID: https://orcid.org/0000-0001-5131-8084)
- Jugal Kishore Sahoo (ORCID: https://orcid.org/0000-0003-2503-9115)
- H. Kreckel
- D. McK. Paul (ORCID: https://orcid.org/0000-0001-7625-4398)
- Leonard W. Isberner (ORCID: https://orcid.org/0000-0002-3571-5765)
- L. Berger (ORCID: https://orcid.org/0000-0001-8226-5528)
- Ábel Kálosi (ORCID: https://orcid.org/0000-0003-3782-0814)
- Aigars Znotins (ORCID: https://orcid.org/0000-0003-2225-6819)
- Oldřich Novotný
- M. Grieser
Institutions
- Justus-Liebig-Universität Gießen (DE)
- Laboratoire Univers et Particules de Montpellier (FR)
- Institut de Physique de Rennes (FR)
- Max Planck Institute for Nuclear Physics (DE)
- UCLouvain (BE)
Publication Details
- Journal
- Astronomy and Astrophysics
- Published
- 2025-06-30
- DOI
- https://doi.org/10.1051/0004-6361/202555316
- Citations
- 4
- Primary Topic
- Astrophysics and Star Formation Studies
- Type
- article
- Field-Weighted Citation Impact
- 4.62
Funders
- Agence Nationale de la Recherche
- Fonds De La Recherche Scientifique - FNRS
- Max-Planck-Gesellschaft
- Université de Montpellier