===== On the Detection of Methyl Mercaptan, CH3SH, in the ISM =====

Methyl mercaptan, or methanethiol, CH<sub>3</sub>SH, was detected in emission with the 7 m Bell Lab telescope toward Sagittarius B2(OH):\\
R. A. Linke, M. A. Frerking, and P. Thaddeus,\\
**[[https://ui.adsabs.harvard.edu/abs/1979ApJ...234L.139L|Interstellar methyl mercaptan]]**\\
//Astrophys. J.// **232**, L139–L142 (1979).\\
6 features belonging to several more //J// = 3 –2 and 4 –3 were observed near 75.9 and near 101 GHz. The derived rotational temperature in that source was about 9 K.\\

Much higher rotational temperatures (about 70 K) were derived in a 3, 2, and 1 mm line survey carried out with SEST:\\
E. Gibb, A. Nummelin, W. M. Irvine, D. C. B. Whittet, and P. Bergman,\\
**[[https://doi.org/10.1086/317805|Chemistry of the Organic-Rich Hot Core G327.3–0.6]]**\\
//Astrophys. J.// **545**, 309–326 (2000).\\

L. Majumdar, P. Gratier, T. Vidal, V. Wakelam, J.-C. Loison, K. M. Hickson, and E. Caux,\\
reported on the\\
**[[https://doi.org/10.1093/mnras/stw457|Detection of CH<sub>3</sub>SH in protostar IRAS 16293-2422]]**\\
//Mon. Not. R. Astron. Soc.// **458**, 1859–1865 (2016).\\
The IRAM 30 m telescope was used to study this solar-type pair of proto-stars at 3 mm. Here, an excitation temperature of 32 ± 4 K was derived.\\

L. F. Rodríguez-Almeida, I. Jiménez-Serra, V. M. Rivilla, J. Martín-Pintado, S. Zeng, B. Tercero, P. de Vicente, Laura Colzi, F. Rico-Villas, S. Martín, and M. A. Requena-Torres\\
reported on\\
**[[https://doi.org/10.3847/2041-8213/abf7cb|Thiols in the Interstellar Medium: First Detection of HC(O)SH and Confirmation of
C<sub>2</sub>H<sub>5</sub>SH]]**\\
//Astrophys. J. Lett.// **912** (2021), Art. No. L11.\\ 
This is the first unumbiguous detection of ethanethiol in the ISM. Ten lines with 2 ≤ //J// ≤ 6 and //K<sub>a</sub>// ≤ 1 were reported and shown, of which nine were unblended or marginally blended and one line was more blended. The observations were part of an unbiased molecular line survey of the quiescent giant molecular cloud G+0.693−0.027, about 1' north-east of Sagittarius B2(N), carried out with the Yebes 40 m dish at 7 mm and with the IRAM 30 m dish at 3 mm. All lines were modeled quite well employing an LTE fit with //T//<sub>rot</sub> = 14.9 ± 0.5 K. The signal-to-noise ratios of the lines were quite good to very good. The column density of methanol is a factor of ∼24 higher.\\


H. S. P. Müller, A. Belloche, L.-H. Xu, R. M. Lees, R. T. Garrod, A. Walters, J. van Wijngaarden, F. Lewen, S. Schlemmer, and K. M. Menten,\\
reported on\\
**[[https://doi.org/10.1051/0004-6361/201527470|Exploring molecular complexity with ALMA (EMoCA): Alkanethiols and alkanols in Sagittarius B2(N2)]]**\\
//Astron. Astrophys.// **587**, Art. No. A92 (2016).\\
A line survey of Sgr B2(N) was carried out with ALMA at 3 mm. CH<sub>3</sub>SH was not only detected in its ground vibrational state, but also in its first torsionally excited state, even though the CH<sub>3</sub>OH/CH<sub>3</sub>SH ratio was only about 120. These authors derived a rotational temperature of 180 K in this source.


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Contributor(s): H. S. P. Müller; 10, 2010; 07, 2016; 05, 2021

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