The Impact Of Hydrogen Atom Tunneling On Aromatic Chemistry In TMC-1
Hydrogen atom tunneling likely plays a substantial role in the gas-phase chemistry of astrochemical environments. To determine the potential effect that it has on the chemical modeling of aromatic molecules, we screened the kida.uva.2024 network, and our own expanded network to find reactions which could be significantly accelerated by hydrogen atom tunneling in the ISM.
In total, 64 reactions were identified. The hydrogen abstraction reactions from H2 to four key interstellar radicals (C2H, OH, CN, and NH2) were studied further using newly calculated potential energy surfaces and RRKM analyses to determine rate coefficients for a temperature of 10 K and a density of 2 × 104 cm−3.
Despite having low rate coefficients of 1.66 × 10−15, 8.17 × 10−16 and 3.15 × 10−16 cm3s−1 the C2H, OH, and CN reactions are competitive in the ISM, due to large overall rates caused by the high abundance of molecular hydrogen. The calculated value for the NH2 reaction, however, was much smaller and found to be inefficient at ISM conditions. The possible effects of all other considered reactions were studied with simulations using calculated collision limit rate coefficients.
Upper and lower bounds were then placed on modeled aromatic abundances using the most significant reactions. Due to the dependence of calculated aromatic abundances on reactions involving c-C6H+5 and the recent questions surrounding its reactivity, we also explored the abundance variations caused by reactions leading to or involving c-C6H+5.
Reace H. J. Willis, Thomas H. Speak, Alex N. Byrne, Christopher N. Shingledecker, Ilsa R. Cooke
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2604.21892 [astro-ph.GA] (or arXiv:2604.21892v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2604.21892
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Related DOI:
https://doi.org/10.3847/1538-4357/ae632c
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Submission history
From: Reace Willis
[v1] Thu, 23 Apr 2026 17:44:06 UTC (3,561 KB)
https://arxiv.org/abs/2604.21892
Astrobiology, Astrochemistry,
