The sulphur saga in TMC-1: Discovery of HCSCN and HCSCCH

Abstract

We report the detection, for the first time in space, of cyano thioformaldehyde (HCSCN) and propynethial (HCSCCH) towards the starless core TMC-1. Cyano thioformaldehyde presents a series of prominent a- and b-type lines, which are the strongest previously unassigned features in our Q-band line survey of TMC-1. Remarkably, HCSCN is four times more abundant than cyano formaldehyde (HCOCN). On the other hand, HCSCCH is five times less abundant than propynal (HCOCCH). Surprisingly, we find an abundance ratio HCSCCH/HCSCN of 0.25, in contrast with most other ethynyl-cyanide pairs of molecules for which the CCH-bearing species is more abundant than the CN-bearing one. We discuss the formation of these molecules in terms of neutral-neutral reactions of S atoms with CH2CCH and CH2CN radicals as well as of CCH and CN radicals with H2CS. The calculated abundances for the sulphur-bearing species are, however, significantly below the observed values, which points to an underestimation of the abundance of atomic sulphur in the model or to missing formation reactions, such as ion-neutral reactions.

Accepted for publication in A&A Letters

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Cited by in corpus (14)

• Discovery of benzyne, o-C6H4, in TMC-1 with the QUIJOTE line survey
• Discovery of the elusive thioketenylium, HCCS+, in TMC-1
• Discovery of C5H+ and detection of C3H+ in TMC-1 with the QUIJOTE line survey
• Discovery of HCCCO and C5O in TMC-1 with the QUIJOTE line survey
• 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 interstellar 3-cyano propargyl radical, CH2CCCN
• Linking the dust and chemical evolution: Taurus and Perseus -- New collisional rates for HCN, HNC, and their C, N, and H isotopologues
• Chemical variations across the TMC-1 boundary: molecular tracers from translucent phase to dense phase
• Laboratory observation and astronomical search of 1-cyano propargyl radical, HCCCHCN
• First detection of HS2 in a cold dark cloud
• 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
• A high-resolution spectroscopic analysis of aminoacrylonitrile and an interstellar search towards G+0.693
• Synthesis and Spectroscopic Characterization of Interstellar Candidate Ethynyl Thiocyanate: HCCSCN