Volume 650, June 2021
|Number of page(s)||5|
|Section||Letters to the Editor|
|Published online||21 June 2021|
Letter to the Editor
Detection of deuterated methylcyanoacetylene, CH2DC3N, in TMC-1⋆
Grupo de Astrofísica Molecular, Instituto de Física Fundamental (IFF-CSIC), C/ Serrano 121, 28006 Madrid, Spain
e-mail: firstname.lastname@example.org; email@example.com
2 LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, 92190 Meudon, France
3 Observatorio Astronómico Nacional (IGN), C/ Alfonso XII, 3, 28014 Madrid, Spain
4 Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
Accepted: 6 June 2021
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+.
Key words: astrochemistry / ISM: molecules / ISM: individual objects: TMC-1 / line: identification / molecular data
© ESO 2021
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