J/A+A/646/L7ivo://CDS.VizieR/J/A+A/646/L7doi:10.26093/cds/vizier.36469007CDSCernicharo 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.2021-07-05T07:24:02Z2021-02-05T07:46:03ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.fratomic-physicsUsing 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, 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 Ju=10 up to Ju=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 500GHz. We derive an abundance ratio N(H_2_CCO)/N(CH_3_CO^+^)~44. The high abundance of the protonated form of H2CCO is due to the high proton affinity of the neutral species. The other isomer, H_2_CCOH^+^, is found to be 178.9kJ/mol 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.2021A&A...646L...7Chttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/646/L7CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/646/L7https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/646/L7http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/646/L7https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/646/L7https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/646/L7http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/646/L7GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/A+A/646/L7/tablee2Predicted frequencies for CH_3_CO^+^recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintJ'Quantum number J for upper levelphys.mol.qnintK'Quantum number K for upper levelphys.mol.qnintJ"Quantum number J for lower levelphys.mol.qnintK"Quantum number K for lower levelphys.mol.qnintFreqFrequencyMHzem.freqdoubleUncUncertainty on frequencyMHzstat.error;em.freqdoubleEupEnergy of the upper levelKphys.energy;phys.atmol.levelfloatAijEinstein Coefficients**-1phys.atmol.transProbdoubleSijLine strengthspect.line.intensitydoubleguDegeneracy of the upper levelphys.electron.degenint