Binding Energies Of Small Interstellar Molecules On Neutral And Charged Amorphous Solid Water Surfaces

The interstellar medium (ISM) is all but empty. To date, more than 300 molecules have already been discovered. Because of the extremely low temperature, the gas-phase chemistry is dominated by barrierless exothermic reactions of radicals and ions.

However, several abundant molecules and organic molecules cannot be produced efficiently by gas-phase reactions. To explain the existence of such molecules in the ISM, gas-surface interactions between small molecules and dust particles covered with amorphous solid water (ASW) mantles must be considered.

Schematic representation of dust grains in the ISM. — astro-ph.GA

In general, surface processes such as adsorption, diffusion, desorption, and chemical reactions can be linked to the binding energy of molecules to the surface. Hence, a lot of studies have been performed to identify the binding energies of interstellar molecules on ASW surfaces.

Cosmic radiation and free electrons may induce a negative charge on the dust particles, and the binding energies may be affected by this charge. In this study, we calculate the binding energies of CO, CH₄, and NH₃, on neutral and charged ASW surfaces using DFT calculations. Our results indicate that CO can interact with the surface charge, increasing its binding energy. In contrast, the binding energy of CH₄ remains unchanged in the presence of surface charge, and that of NH₃ typically decreases.

Tobe Vorsselmans, Erik C. Neyts

Comments: This is the Accepted Manuscript version of an article accepted for publication in The Astrophysical Journal. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. This Accepted Manuscript is published under a CC BY licence. The Version of Record is available online at DOI: https://doi.org/10.3847/1538-4357/add145
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2506.01431 [astro-ph.GA] (or arXiv:2506.01431v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2506.01431
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Related DOI:
https://doi.org/10.3847/1538-4357/add145
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Submission history
From: Tobe Vorsselmans
[v1] Mon, 2 Jun 2025 08:41:48 UTC (1,638 KB)
https://arxiv.org/abs/2506.01431
Astrobiology, Astrochemistry,