New deuterated species in TMC-1: Detection of CH2DC4H with the QUIJOTE line survey

Abstract

We report the first detection in space of the single deuterated isotopologue of methyldiacetylene, CH2DC4H. A total of 12 rotational transitions, with J = 8-12 and Ka = 0 and 1, were identified for this species in TMC-1 in the 31.0-50.4 GHz range using the Yebes 40m radio telescope. The observed frequencies allowed us to obtain, for the first time, the spectroscopic parameters of this deuterated isotopologue. We derived a column density of (5.5+/-0.2)e11 cm-2. The abundance ratio between CH3C4H and CH2DC4H is 24+/-2. This ratio is similar to that found for the CH3C3N/CH2DC3N analogue system, which is 22+/-2.We did not detect the deuterated species CH3C4D, which has already been observed in laboratory experiments. The detection of deuterated CH3C4H allows us to extend the discussion on the chemical mechanisms of deuterium fractionation at work in TMC-1 using a new gas-phase chemical model with multiply deuterated molecules. Introducing a possible deuterium exchange reaction between CH3CCH and atomic deuterium allows us to account for the CH3C4H/CH2DC4H abundance ratio.

Accepted for publication in A&A Letters on December 20th. arXiv admin note: text overlap with arXiv:2106.03404

References in corpus (12)

• Pure hydrocarbon cycles in TMC-1: Discovery of ethynyl cyclopropenylidene, cyclopentadiene and indene
• Discovery of benzyne, o-C6H4, in TMC-1 with the QUIJOTE line survey
• Yebes 40 m radio telescope and the broad band NANOCOSMOS receivers at 7 mm and 3 mm for line surveys
• Discovery of the propargyl radical (CH2CCH) in TMC-1: one of the most abundant radicals ever found and a key species for cyclization to benzene in cold dark clouds
• Discovery of HC3O+ in space: The chemistry of O-bearing species in TMC-1
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• Cumulene carbenes in TMC-1: Astronomical discovery of $l$-H${}_2$C${}_5$
• Space and laboratory observation of the deuterated cyanomethyl radical HDCCN
• Interstellar detection of the simplest aminocarbyne, H2NC: an ignored but abundant molecule
• Discovery of interstellar 3-cyano propargyl radical, CH2CCCN
• Detection of deuterated methylcyanoacetylene, CH${}_2$DC${}_3$N, in TMC-1
• First detection of doubly deuterated methyl acetylene (CHD2CCH and CH2DCCD)

Cited by in corpus (5)

• Discovery of fulvenallene in TMC-1 with the QUIJOTE line survey
• Discovery of thiofulminic acid with the QUIJOTE line survey: A study of the isomers of HNCS and HNCO in TMC-1
• Discovery of a new molecular ion, HC7NH+, in TMC-1
• Doubly substituted isotopologues of HCCCN in TMC-1: Detection of D13CCCN, DC13CCN, DCC13CN, DCCC15N, H13C13CCN, H13CC13CN, HC13C13CN, HCC13C15N, and HC13CC15N
• Direct D-atom incorporation in radicals: An overlooked pathway for deuterium fractionation