Letter to the Editor

Space and laboratory observation of the deuterated cyanomethyl radical HDCCN^⋆,⋆⋆

¹ Grupo de Astrofísica Molecular, Instituto de Física Fundamental (IFF-CSIC), C/ Serrano 121, 28006 Madrid, Spain
e-mail: carlos.cabezas@csic.es; jose.cernicharo@csic.es
² Department of Applied Chemistry, Science Building II, National Chiao Tung University, 1001 Ta-Hsueh Rd., Hsinchu 30010, Taiwan
³ LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, 92190 Meudon, France
⁴ Observatorio Astronómico Nacional (IGN), C/ Alfonso XII, 3, 28014 Madrid, Spain
⁵ Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain

Received: 22 December 2020
Accepted: 10 January 2021

Abstract

Our observations of TMC-1 with the Yebes 40 m radio telescope in the 31.0–50.3 GHz range allowed us to detect a group of unidentified lines, showing a complex line pattern indicative of an open-shell species. The observed frequencies of these lines and the similarity of the spectral pattern with that of the 2_0, 2–1_0, 1 rotational transition of H₂CCN indicate that the lines arise from the deuterated cyanomethyl radical, HDCCN. Using Fourier transform microwave spectroscopy experiments combined with electric discharges, we succeeded in producing the radical HDCCN in the laboratory and observed its 1_0, 1–0_0, 0 and 2_0, 2–1_0, 1 rotational transitions. From our observations and assuming a rotational temperature of 5 K, we derive an abundance ratio H₂CCN/HDCCN = 20 ± 4. The high abundance of the deuterated form of H₂CCN is well accounted for by a standard gas-phase model, in which deuteration is driven by deuteron transfer from the H₂D⁺ molecular ion.