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

TL;DR

This study reports the discovery of two new molecules, CH2CCHC4H and CH2CCHC3N, in the TMC-1 prestellar core using the QUIJOTE survey, providing detailed spectroscopic and abundance analysis consistent with chemical models.

Contribution

First detection of CH2CCHC4H and rigorous detection of CH2CCHC3N in TMC-1, with detailed spectroscopic parameters and abundance comparison to isomers and models.

Findings

Detected 20 rotational transitions for each molecule.

Column densities are approximately 2.2x10^12 and 1.2x10^11 cm^-2.

Rotational temperature of 9.0 K for both species.

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 Ju=17 up to 24 and Ka<=3. The column density for CH2CCHC4H is N=(2.2+/-0.2)x 1E12 cm-2, while for CH2CCHC3N, we derived N=(1.2+/-0.15) x 1E11 cm-2. The rotational temperature is 9.0+/-0.5 K for both species. The abundance ratio between 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=20-19 up to J=30-29 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.