Letter to the Editor

Discovery of CH₂CHCCH and detection of HCCN, HC₄N, CH₃CH₂CN, and, tentatively, CH₃CH₂CCH in TMC-1^⋆

¹ Grupo de Astrofísica Molecular, Instituto de Física Fundamental (IFF-CSIC), C/ Serrano 121, 28006 Madrid, Spain
e-mail: jose.cernicharo@csic.es
² Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
³ Observatorio Astronómico Nacional (IGN), C/ Alfonso XII, 3, 28014 Madrid, Spain

Received: 28 January 2021
Accepted: 15 February 2021

Abstract

We present the discovery in TMC-1 of vinyl acetylene, CH₂CHCCH, and the detection, for the first time in a cold dark cloud, of HCCN, HC₄N, and CH₃CH₂CN. A tentative detection of CH₃CH₂CCH is also reported. The column density of vinyl acetylene is (1.2 ± 0.2) × 10¹³ cm⁻², which makes it one of the most abundant closed-shell hydrocarbons detected in TMC-1. Its abundance is only three times lower than that of propylene, CH₃CHCH₂. The column densities derived for HCCN and HC₄N are (4.4 ± 04) × 10¹¹ cm⁻² and (3.7 ± 0.4) × 10¹¹ cm⁻², respectively. Hence, the HCCN/HC₄N abundance ratio is 1.2 ± 0.3. For ethyl cyanide we derive a column density of (1.1 ± 0.3) × 10¹¹ cm⁻². These results are compared with a state-of-the-art chemical model of TMC-1, which is able to account for the observed abundances of these molecules through gas-phase chemical routes.