Proposed Importance Of HOCO Chemistry: Inefficient Formation Of CO2 From CO And OH Reactions On Ice Dust

With the advent of JWST ice observations, dedicated studies on the formation reactions of detected molecules are becoming increasingly important. One of the most interesting molecules in interstellar ice is CO₂.

Despite its simplicity, the main formation reaction considered, CO + OH -> CO₂ + H through the energetic HOCO* intermediate on ice dust, is subject to uncertainty because it directly competes with the stabilization of HOCO as a final product which is formed through energy dissipation of HOCO* to the water ice. When energy dissipation to the surface is effective during reaction, HOCO can be a dominant product.

In this study, we experimentally demonstrate that the major product of the reaction is indeed not CO₂, but rather the highly reactive radical HOCO. The HOCO radical can later evolve into CO₂ through H-abstraction reactions, but these reactions compete with addition reactions, leading to the formation of carboxylic acids (R-COOH).

Our results highlight the importance of HOCO chemistry and encourage further exploration of the chemistry of this radical.

Atsuki Ishibashi, Germán Molpeceres, Hiroshi Hidaka, Yasuhiro Oba, Thanja Lamberts, Naoki Watanabe

Comments: Accepted in ApJ; 23 pages, 9 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2410.01373 [astro-ph.GA] (or arXiv:2410.01373v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2410.01373
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Submission history
From: Atsuki Ishibashi
[v1] Wed, 2 Oct 2024 09:37:41 UTC (6,585 KB)
https://arxiv.org/abs/2410.01373

Astrobiology, Astrochemistry, Astronomy,