Letter to the Editor

Discovery of CH₂CCHC₄H and a rigorous detection of CH₂CCHC₃N in TMC-1 with the QUIJOTE line survey^⋆,⋆⋆

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

Received: 25 April 2022
Accepted: 6 June 2022

Abstract

Using the QUIJOTE line survey in the 32.0–50.4 GHz range, we report the discovery of the molecule CH₂CCHC₄H towards the prestellar cold core TMC-1 in the Taurus region. We also present a rigorous detection of CH₂CCHC₃N, along with its detailed analysis. We identified a total of twenty rotational transitions for each one of these molecules. The rotational quantum numbers range from J_u = 17 up to 24 and K_a≤ 3. The column density for CH₂CCHC₄H is N = (2.2 ± 0.2) × 10¹² cm⁻², while for CH₂CCHC₃N, we derived N = (1.2 ± 0.15) × 10¹¹ cm⁻². The rotational temperature is 9.0 ± 0.5 K for both species. The abundance ratiobetween CH₂CCHC₄H and CH₂CCHC₃N is 18 ± 4. We also compared the column densities of these species with those of their isomers CH₃C₆H and CH₃C₅N, derived from their J = 20 − 10 up to J = 31 − 30 rotational transitions observed with the QUIJOTE line survey. The observed abundances for all these species are reasonably well explained by state-of-the-art chemical models of TMC-1. The observed astronomical frequencies were merged with laboratory frequencies from the literature to derive improved spectroscopic parameters.