Discovery Of Linear Propadienone: Study Of The Chemistry Of Linear And Cyclic H2C3O And H2C3S In TMC-1

We report the first detection in space of propadienone, the linear isomer (l-H₂C₃O) of cyclopropenone (c-H₂C₃O).

We also report the first detection of the isotopologue c-H₂¹³CCCO, and c-HDCCCO of c-H₂C₃O. The astronomical observations are part of QUIJOTE, a line survey of TMC-1 in the frequency range 31.0-50.3 GHz, complemented with data between 71.6-116.0 GHz, and carried out with Yebes-40m and IRAM-30m telescopes, respectively.

We obtain a total column density of 3.7×10¹⁰ cm⁻² for l-H₂C₃O at an excitation temperature of 4.8 K. We find that the isomer is about eight times less abundant than the cyclic one. We also report a detailed line-by-line study of cyclopropenethione (c-H₂C₃S) to compare the abundance of the O and S isomers.

We find that cyclic O-isomers are more abundant than cyclic S-isomers; however, the opposite trend is found for the most stable linear isomers, with l-H₂C₃S being more than one order of magnitude more abundant than l-H₂C₃O. A comprehensive theoretical chemical analysis shows that the abundances of the H₂C₃O and H₂C₃S isomers are controlled by different formation pathways.

In particular, while l-HH₂C₃O is potentially produced by dissociative electron recombination reactions, ion-neutral chemistry is more effective at producing l-H₂C₃S and c-H₂C₃S.

G. Esplugues, J. C. Loison, M. Agúndez, G. Molpeceres, N. Marcelino, B. Tercero, J. Cernicharo

Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2511.19775 [astro-ph.GA] (or arXiv:2511.19775v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2511.19775
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Related DOI:
https://doi.org/10.1051/0004-6361/202557355
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Submission history
From: Gisela Esplugues Dr
[v1] Mon, 24 Nov 2025 23:00:20 UTC (1,457 KB)
https://arxiv.org/abs/2511.19775

Astrobiology, Astrochemistry,