Detection of deuterated methylcyanoacetylene, CH2DC3N, in TMC-1
Abstract
We report the first detection in space of the single deuterated isotopologue of methylcyanoacetylene, CH2DC3N. A total of 15 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 40 m radio telescope. The observed frequencies were used to derive for the first time the spectroscopic parameters of this deuterated isotopologue. We derive a column density of (8.0 ± 0.4)×1010 cm−2. The abundance ratio of CH3C3N to CH2DC3N is ∼22. We also theoretically computed the principal spectroscopic constants of 13C isotopologues of CH3C3N and CH3C4H and those of the deuterated isotopologues of CH3C4H for which we could expect a similar degree of deuteration enhancement. However, we have not detected either CH2DC4H or CH3C4D, nor any 13C isotopologues. The different observed deuterium ratios in TMC-1 are reasonably accounted for by a gas-phase chemical model where the low temperature conditions favour deuteron transfer through reactions with H2D+.
Based on observations carried out with the Yebes 40 m telescope (projects 19A003, 20A014, and 20D15). The 40 m radiotelescope at Yebes Observatory is operated by the Spanish Geographic Institute (IGN, Ministerio de Transportes, Movilidad y Agenda Urbana).- Publication:
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Astronomy and Astrophysics
- Pub Date:
- June 2021
- DOI:
- 10.1051/0004-6361/202141371
- arXiv:
- arXiv:2106.03404
- Bibcode:
- 2021A&A...650L..15C
- Keywords:
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- astrochemistry;
- ISM: molecules;
- ISM: individual objects: TMC-1;
- line: identification;
- molecular data;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Accepted for publication in A&