Gas-phase Formation Routes Of Dimethyl Sulfide In The Interstellar Medium

Context: Dimethyl sulfide (DMS; CH₃SCH₃) is an organosulfur compound that has been suggested as a potential biosignature in exoplanetary atmospheres. In addition to its tentative detections toward the sub-Neptune planet K2-18b, DMS has been detected in the coma of the 67/P comet and toward the galactic center molecular cloud G+0.693-0.027. However, its formation routes have not been characterized yet.

Aims: In this work, we have investigated three gas-phase reactions (CH₃SH + CH₃OH⁺², CH₃OH ⁺ CH₃SH⁺², and the CH₃ + CH₃S radiative association), aiming at characterizing DMS formation routes in shocked molecular clouds and star-forming regions. Methods: We have performed dedicated quantum and kinetics calculations to evaluate the reaction rate coefficients as a function of temperature to be included in astrochemical models.

Results: Among the investigated processes, the reaction between methanethiol (CH₃SH) and protonated methanol (CH₃OH⁺²)(possibly followed by a gentle proton transfer to ammonia) is a compelling candidate to explain the formation of DMS in the galactic center molecular cloud G+0.693-0.027. The CH₃ + CH₃S radiative association does not seem to be a very efficient process, with the exclusion of cold clouds, provided that the thiomethoxy radical (CH₃S) is available.

This work does not deal directly with the possible formation of DMS in the atmosphere of exoplanets. However, it clearly indicates that there are efficient abiotic formation routes of this interesting species.

Gabriella Di Genova, Nadia Balucani, Luca Mancini, Marzio Rosi, Dimitrios Skouteris, Cecilia Ceccarelli

Subjects: Astrophysics of Galaxies (astro-ph.GA); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR); Chemical Physics (physics.chem-ph)
Cite as: arXiv:2504.16236 [astro-ph.GA] (or arXiv:2504.16236v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2504.16236
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Submission history
From: Nadia Balucani
[v1] Tue, 22 Apr 2025 20:03:29 UTC (671 KB)
https://arxiv.org/abs/2504.16236
Astrobiology, Astrochemistry,