Thioxoethenylidene, C2S, and Thioxopropadienylidene, C3S

N. Kaifu, H. Suzuki, M. Ohishi, T. Miyaki, S.-I. Ishikawa, T. Kasuga, M. Morimoto, and S. Saito
reported on the
Detection of Intense Unidentified Lines in TMC-1
Astrophys. J. 317, L111–L114 (1987);
obtained in the course of a molecular line survey carried out with the 45 m Nobeyama telescope which ultimately covered the 8 – 50 GHz range.

Laboratory spectroscopic investigations by
S. Saito, K. Kawaguchi, S. Yamamoto, M. Ohishi, H. Suzuki, and N. Kaifu
lead to the
Laboratory Detection and Astronomical Identification of a New Free Radical, CCS <sup>3</sup>Σ<sup>–</sup>
Astrophys. J. 317, L115–L118 (1987).
Four lines from the line survey mentioned above were assigned to C2S. These were the NJ = 12 – 21, 33 – 22, 43 – 32, and 34 – 23 transitions at 22344, 38866, 43981, and 45379 MHz, respectively. Please note: the labeling of the 21 level follows that of the CDMS catalog entry. This level is labeled 01 in the original work.
The authors also assigned several U-lines from two molecular line surveys of Sagittarius B2 in the 3 and 2 mm regions to C2S.
Finally, the CC34S isotopolog was also detected toward TMC-1 by its 12 – 21 transition at 21930 MHz.

In addition, laboratory spectroscopic investigations by
S. Yamamoto, S. Saito, K. Kawaguchi, N. Kaifu, and H. Suzuki
lead to the
Laboratory Detection of a New Carbon-chain Molecule C<sub>3</sub>S and its Astronomical Identification
Astrophys. J. 317, L119–L121 (1987).
The J = 4 – 3, 7 – 6, and 8 – 7 transitions were identified at 23123, 40465, and 46246 MHz, respectively.

Additional information on C2S

C2S, along with C3S, were also detected with the IRAM 30 m telescope in the circumstellar envelope of the carbon-rich late-type star CW Leo, also known as IRC +10216 in the course of a molecular line survey in the 3 and 2 mm regions by
J. Cernicharo, M. Guélin, H. Hein, and C. Kahane,
Sulfur in IRC +10216
Astron. Astrophys. 181, L9–L12 (1987).

C2S was also seen toward several translucent clouds, albeit in only the lower energy transition of two by
B. E. Turner, H.-H. Lee, and E. Herbst,
The Physics and Chemistry of Small Translucent Molecular Clouds.\\ IX. Acetylenic Chemistry
Astrophys. J. Suppl. Ser. 115, 91–118 (1998).

The two 13C isotopomers were detected with the Nobeyama 45 m telescope toward TMC-1 by
N. Sakai, M. Ikeda, M. Morita, T. Sakai, S. Takano, Y. Osamura, and S. Yamamoto,
Production Pathways of CCS and CCCS Inferred from Their <sup>13</sup>C Isotopic Species
Astrophys. J. 663, 1174–1179 (2007).
The C13CS isotopolog is highly depleted, and it has not been detected in L1521E, whereas 13CCS was seen.

Additional information on C3S

C3S, along with C2S, were also detected with the IRAM 30 m telescope in the circumstellar envelope of the carbon-rich late-type star CW Leo, also known as IRC +10216 in the course of a molecular line survey in the 3 and 2 mm region by
J. Cernicharo, M. Guélin, H. Hein, and C. Kahane,
Sulfur in IRC +10216
Astron. Astrophys. 181, L9–L12 (1987).

The detection of the 34S isotopolog in the course of the Nobeyama 45 m line survey was mentioned first by
M. Ohishi and N. Kaifu,
Chemical and Physical Evolution of Dark Clouds. Molecular Spectral Line Survey toward TMC-1
Faraday Discuss. 190, 205–216 (1998).

C3S was deteceted very recently in a warm cloud by
B. Tercero, J. Cernicharo, J. R. Pardo, and J. R. Goicoechea,
A line confusion limited millimeter survey of Orion KL\\ I. Sulfur carbon chains
Astron. Astrophys. 517, Art. No. A96 (2010).


Information on thioxopentatetraenylidene, C5S

M. Agúndez, J. Cernicharo, and M. Guélin
reported on
New molecules in IRC +10216: confirmation of C<sub>5</sub>S and tentative identification of MgCCH, NCCP, and SiH<sub>3</sub>CN
Astron. Astrophys. 570, Art. No. A45 (2014).
The J + 1 → J transitions with J = 43, 44, and 45 of C5S were identified in the course of a 3 mm line survey with the IRAM 30 m telescope near 81.2, 83.0, and 84.9 GHz. The first transition is blended. The identification rests to a considerable amount on an earlier report detailed below that is deemed to be not secure. Therefore, we suggest to view the identification of C5S in space with some caution. The almost similar column densities between two carbon chain molecules, here C5S and C3S, are very unusual, though not unprecedented.

M. B. Bell, L. W. Avery, and P. A. Feldman
had reported on
C<sub>3</sub>S and C<sub>5</sub>S in IRC +10216
Astrophys. J. 417, L37–L40 (1993).
A line observed with the NRAO 43 m telecope near 24.0 GHz in the course of a molecular line survey was assigned to the J = 13 – 12 transition of C5S. The authors state in the abstract: “Assuming the observed feature is due to C5S, we find that N(C5S)/N(C3S) ≈ 0.5.” Confirmation of this finding or identification of further transitions at shorter wavelengths will be useful.


Information on C4S and larger species

Thioxobutatrienylidene, C4S, and larger molecules CnS, with n ≥ 6, have not been detected in space thus far.


Contributor(s): H. S. P. Müller; 09, 2012; 07, 2018; 09, 2020


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