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arXiv · 2112.11855

Discovery of the elusive thioketenylium, HCCS+, in TMC-1

C. Cabezas·M. Agundez·N. Marcelino·B. Tercero·Y. Endo·R. Fuentetaja·J. R. Pardo·P. de Vicente·J. Cernicharo
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Abstract

We report the detection in TMC-1 of the cation HCCS+ (3Sigma-), which is the protonated form of the widespread radical CCS. This is the first time that a protonated radical has been detected in a cold dark cloud. Twenty-six hyperfine components from twelve rotational transitions have been observed with the Yebes 40m and IRAM 30m radio telescopes. We confidently assign the characteristic rotational spectrum pattern to HCCS+ based on the good agreement between the astronomical and theoretical spectroscopic parameters. The column density of HCCS+ is (1.1+/-0.1)e12 cm-2, and the CCS/HCCS+ abundance ratio is 50+/-10, which is very similar to that of CS/HCS+ (35+/-8) and CCCS/HCCCS+ (65+/-20). From a state-of-the-art gas-phase chemical model, we conclude that HCCS+ is mostly formed by reactions of proton transfer from abundant cations such as HCO+, H3O+, and H3+ to the radical CCS.

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C. Cabezas, M. Agundez, N. Marcelino, B. Tercero, Y. Endo, R. Fuentetaja, J. R. Pardo, P. de Vicente, J. Cernicharo. 2021-12-22. Discovery of the elusive thioketenylium, HCCS+, in TMC-1. https://doi.org/10.1051/0004-6361%2F202142815

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