J/A+A/646/L7 CH3CO+ discovery in space and in laboratory (Cernicharo+, 2021)
Discovery of the acetyl cation, CH3CO+, in space and in the laboratory.
Cernicharo J., Cabezas C., Bailleux S., Margules L., Motiyenko R., Zou L.,
Endo Y., Bermudez C., Agundez M., Marcelino N., Lefloch B., Tercero B.,
de Vicente P.
<Astron. Astrophys. 646, L7 (2021)>
=2021A&A...646L...7C 2021A&A...646L...7C (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics
Keywords: astrochemistry - ISM: molecules - ISM: individual: TMC-1 -
line: identification - molecular data
Abstract:
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 500GHz. 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
178.9kJ/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.
Description:
tablee2.dat contains rotational transitions for CH3CO+ up to
Emax=2000K.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablee2.dat 74 783 Predicted frequencies for CH3CO+
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Byte-by-byte Description of file: tablee2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- J' Quantum number J for upper level
5- 6 I2 --- K' Quantum number K for upper level
9- 10 I2 --- J" Quantum number J for lower level
13- 14 I2 --- K" Quantum number K for lower level
17- 29 F13.5 MHz Freq Frequency
34- 40 F7.5 MHz Unc Uncertainty on frequency
43- 48 F6.1 K Eup Energy of the upper level
50- 58 E9.4 s-1 Aij Einstein Coefficient
61- 68 F8.4 --- Sij Line strength
72- 74 I3 --- gu Degeneracy of the upper level
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Acknowledgements:
Jose Cernicharo, jose.cernicharo(at)csic.es
(End) Patricia Vannier [CDS] 13-Jan-2021