Discovery of two new interstellar molecules with QUIJOTE: HCCCHCCC and HCCCCS

Abstract

We report on the discovery of two new molecules, HCCCHCCC and HCCCCS, towards the starless core TMC-1 in the Taurus region from the QUIJOTE line survey in the 31.1-50.2 GHz frequency range. We identify a total of twenty-nine lines of HCCCHCCC and six rotational transitions of HCCCCS. The rotational quantum numbers range from Ju=10 up to 15 and Ka <=2 for HCCCHCCC and Ju=21/2 up to 31/2 for HCCCCS. We derived a column density for HCCCHCCC of N=(1.3+/-0.2)x10^11 cm-2 with a rotational temperature of 6+/-1 K, while for HCCCCS we derived N=(9.5+/-0.8)x10^10 cm-2 and Trot =10+/-1 K. The abundance of HCCCHCCC is higher than that of its recently discovered isomer, l-H2C6. If we compare HCCCCS with its related molecules, HCS and HCCS, we obtain abundance ratios HCS/HCCCCS=58 and HCCS/HCCCCS=7.2. We investigated the formation of these two molecules using chemical modelling calculations. The observed abundances can be accounted for by assuming standard gas-phase formation routes involving neutral-neutral reactions and ion-neutral reactions.

arXiv admin note: text overlap with arXiv:2206.08992

References in corpus (12)

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Cited by in corpus (7)

• Carbon-Chain Chemistry in the Interstellar Medium
• Discovery of thiofulminic acid with the QUIJOTE line survey: A study of the isomers of HNCS and HNCO in TMC-1
• Laboratory and astronomical discovery of cyanothioketene, NCCHCS, in the cold starless core TMC-1
• Discovery of CH3CHCO in TMC-1 with the QUIJOTE line survey
• Linking the dust and chemical evolution: Taurus and Perseus -- New collisional rates for HCN, HNC, and their C, N, and H isotopologues
• Gas phase Elemental abundances in Molecular cloudS (GEMS) VIII. Unlocking the CS chemistry: the CH + S$\to$ CS + H and C${}_2$ + S$\to$ CS + C reactions
• Synthesis and Spectroscopic Characterization of Interstellar Candidate Ethynyl Thiocyanate: HCCSCN