Discovery Of The Acetyl Cation, CH3CO+, In Space And In The Laboratory

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Acetyl Cation, CH3CO+

Using the Yebes 40m and IRAM 30m radiotelescopes, we detected two series of harmonically related lines in space that can be fitted to a symmetric rotor. The lines have been seen towards the cold dense cores TMC-1, L483, L1527, and L1544.

High level of theory ab initio calculations indicate that the best possible candidate is the acetyl cation, CH3CO+, which is the most stable product resulting from the protonation of ketene. We have produced this species in the laboratory and observed its rotational transitions Ju = 10 up to Ju = 27.

Hence, we report the discovery of CH3CO+ in space based on our observations, theoretical calculations, and laboratory experiments. The derived rotational and distortion constants allow us to predict the spectrum of CH3CO+ with high accuracy up to 500 GHz. We derive an abundance ratio N(H2CCO)/N(CH3CO+) = 44. The high abundance of the protonated form of H2CCO is due to the high proton affinity of the neutral species.

The other isomer, H2CCOH+, is found to be 178.9 kJ/mol above CH3CO+. The observed intensity ratio between the K=0 and K=1 lines, 2.2, strongly suggests that the A and E symmetry states have suffered interconversion processes due to collisions with H and/or H2, or during their formation through the reaction of H3+ with H2CCO.

J. Cernicharo, C. Cabezas, S. Bailleux, L. Margules, R. Motiyenko, L. Zou, Y. Endo, C. Bermudez, M. Agundez, N. Marcelino, B. Lefloch, B. Tercero, P. de Vicente

Comments: Accepted for publication in A&A Letters
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2101.04603 [astro-ph.GA] (or arXiv:2101.04603v1 [astro-ph.GA] for this version)
Submission history
From: Marcelino Agundez
[v1] Tue, 12 Jan 2021 17:03:11 UTC (1,003 KB)
https://arxiv.org/abs/2101.04603
Astrobiology, Astrochemistry,

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