Laboratory And Astronomical Discovery Of Cyanothioketene, NCCHCS, In The Cold Starless Core TMC-1

By Keith Cowing
Status Report
May 6, 2024
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Laboratory And Astronomical Discovery Of Cyanothioketene, NCCHCS, In The Cold Starless Core TMC-1
Optimized molecular structure of cyanothioketene as obtained from quantum chemical calculations. — astro-ph.GA

We present the detection of cyanothioketene, NCCHCS, in the laboratory and toward TMC-1. This transient species was produced through a discharge of a gas mixture of CH2CHCN and CS2 using argon as carrier gas, and its rotational spectrum between 9 and 40 GHz was characterized using a Balle-Flygare narrowband-type Fourier-transform microwave spectrometer.

A total of 21 rotational transitions were detected in the laboratory, all of them exhibiting hyperfine structure induced by the spin of the N nucleus. The spectrum for NCCHCS was predicted in the domain of our line surveys using the derived rotational and distortion constants. The detection in the cold starless core TMC-1 was based on the QUIJOTE line survey performed with the Yebes 40m radio telescope. Twenty-three lines were detected with K_a=0, 1, and 2 and J_u=9 up to 14.

The derived column density is (1.2+/-0.1)e11 cm-2 for a rotational temperature of 8.5+/-1 K. The abundance ratio of thioketene and its cyano derivative, H2CCS/NCCHCS, is 6.5+/-1.3. Although ketene is more abundant than thioketene by about 15 times, its cyano derivative NCCHCO surprisingly is not detected with a 3sigma upper level to the column density of 3.0e10 cm-2, which results in an abundance ratio H2CCO/NCCHCO > 430.

Hence, the chemistry of CN derivatives seems to be more favored for S-bearing than for O-bearing molecules. We carried out chemical modeling calculations and found that the gas-phase neutral-neutral reactions CCN + H2CS and CN + H2CCS could be a source of NCCHCS in TMC-1.

C. Cabezas, M. Agúndez, Y. Endo, B. Tercero, Y.-P. Lee, N. Marcelino, P. de Vicente, J. Cernicharo

Comments: Accepted as a Letter in Astronomy & Astrophysics on May 2nd 2024. arXiv admin note: text overlap with arXiv:2311.13860, arXiv:2404.07585
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2405.02033 [astro-ph.GA] (or arXiv:2405.02033v1 [astro-ph.GA] for this version)
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From: Carlos Cabezas
[v1] Fri, 3 May 2024 12:10:35 UTC (266 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻