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Discovery of the acetyl cation, CH3CO+, in space and in the laboratory

Abstract : Using the Yebes 40 m and IRAM 30 m 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, CH 3 CO + , 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 J u = 10 up to J u = 27. Hence, we report the discovery of CH 3 CO + in space based on our observations, theoretical calculations, and laboratory experiments. The derived rotational and distortion constants allow us to predict the spectrum of CH 3 CO + with high accuracy up to 500 GHz. We derive an abundance ratio N(H 2 CCO)/N(CH 3 CO +) ∼ 44. The high abundance of the protonated form of H 2 CCO is due to the high proton affinity of the neutral species. The other isomer, H 2 CCOH + , is found to be 178.9 kJ mol −1 above CH 3 CO +. 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 H 2 , or during their formation through the reaction of H + 3 with H 2 CCO.
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https://hal-cnrs.archives-ouvertes.fr/hal-03381420
Contributor : Bertrand Le Floch Connect in order to contact the contributor
Submitted on : Saturday, October 16, 2021 - 5:30:15 PM
Last modification on : Tuesday, October 19, 2021 - 10:59:24 AM

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J Cernicharo, C Cabezas, S Bailleux, L Margulès, R Motiyenko, et al.. Discovery of the acetyl cation, CH3CO+, in space and in the laboratory. Astronomy and Astrophysics - A&A, EDP Sciences, 2021, 646, ⟨10.1051/0004-6361/202040076⟩. ⟨hal-03381420⟩

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