Formation Of Interstellar Complex Organic Molecules On Water-rich Ices Triggered By Atomic Carbon Freezing

By Keith Cowing
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January 30, 2024
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Formation Of Interstellar Complex Organic Molecules On Water-rich Ices Triggered By Atomic Carbon Freezing
The (H2O)20 cluster model used in this work, optimised at ωB97X-V/def2-TZVP, which also shows the size dimensions. The different positions in which the C atom has been adsorbed (Pos1, Pos2, and Pos3) are also shown. — astro-ph.GA

The reactivity of interstellar carbon atoms (C) on the water-dominated ices is one of the possible ways to form interstellar complex organic molecules (iCOMs).

In this work, we report a quantum chemical study of the coupling reaction of C (3P) with an icy water molecule, alongside possible subsequent reactions with the most abundant closed shell frozen species (NH3, CO, CO2 and H2), atoms (H, N and O), and molecular radicals (OH, NH2 and CH3). We found that C spontaneously reacts with the water molecule, resulting in the formation of 3C-OH2, a highly reactive species due to its triplet electronic state.

While reactions with the closed-shell species do not show any reactivity, reactions with N and O form CN and CO, respectively, the latter ending up into methanol upon subsequent hydrogenation. The reactions with OH, CH3 and NH2 form methanediol, ethanol and methanimine, respectively, upon subsequent hydrogenation. We also propose an explanation for methane formation, observed in experiments through H additions to C in the presence of ices.

The astrochemical implications of this work are: i) atomic C on water ice is locked into 3C-OH2, making difficult the reactivity of bare C atoms on the icy surfaces, contrary to what is assumed in astrochemical current models; and ii) the extraordinary reactivity of 3C-OH2 provides new routes towards the formation of iCOMs in a non-energetic way, in particular ethanol, mother of other iCOMs once in the gas-phase.

Stefano Ferrero, Cecilia Ceccarelli, Piero Ugliengo, Mariona Sodupe, Albert Rimola

Subjects: Astrophysics of Galaxies (astro-ph.GA); Chemical Physics (physics.chem-ph)
Cite as: arXiv:2310.14831 [astro-ph.GA] (or arXiv:2310.14831v1 [astro-ph.GA] for this version)
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Submission history
From: Stefano Ferrero [view email]
[v1] Mon, 23 Oct 2023 11:49:37 UTC (2,805 KB)
Astrobiology, Astrochemistry,

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻