===== On Ethyl Mercaptan, C2H5SH, in the ISM =====

L. Kolesniková, B. Tercero, J. Cernicharo, J. L. Alonso, A. M. Daly, B. P. Gordon, and S. T. Shipman,\\
reported on the\\
**[[https://doi.org/10.1088/2041-8205/784/1/L7|Spectroscopic Characterization and Detection of Ethyl Mercaptan in Orion]]**\\
//Astrophys. J.// **784**, Art. No. L7 (2014).\\
A plethora of features identified in a molecular line survey of Orion KL in the 3, 2, and 1.3 mm range with the IRAM 30 m radiotelescope were ascribed to the lower energy //gauche// conformer. However, the number of isolated transitions assigned at least mainly to //g//-C<sub>2</sub>H<sub>5</sub>SH is fairly small, the overwhelming majority of the lines are heavily blended and often close to the confusion limit. In addition, a large fraction of the emission features remains at least partially unassigned. Moreover, the deduced column density compared to that of CH<sub>3</sub>SH as well as that of C<sub>2</sub>H<sub>5</sub>OH are surprisingly high. Therefore, we recommend to view the detection with some caution.

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. Stringent upper limits were derived to the column density of ethanethiol with ratios CH<sub>3</sub>SH/C<sub>2</sub>H<sub>5</sub>SH and C<sub>2</sub>H<sub>5</sub>OH/C<sub>2</sub>H<sub>5</sub>SH of larger than about 21 and 125, respectively. However, these findings, as well as concurrently presented chemical modeling do not permit a strict statement concerning the above report on ethanethiol in Orion KL.\\
The authors noted, however, that one of the few clearer lines attributed to ethanethiol leaves only room for a column density of zero in Orion KL. Also, this line may explain that the reported column density is compatible with zero within two times the uncertainty. Thus, better observational results are needed before ethanethiol may be viewed as unambiguously detected species.\\

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 meanwhile 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 of the lower-lying gauche conformer with 3 ≤ //J// ≤ 10 and //K<sub>a</sub>// ≤ 3 were reported and shown, of which six were unblended or marginally blended, four lines were 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 but one of the blended lines were modeled quite well employing an LTE fit with //T//<sub>rot</sub> ≈ 10 K. The column density of methanethiol is a factor of ∼16 higher, that of ethanol a factor of ∼15 higher.\\



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Contributor(s): H. S. P. Müller; 06, 2014; 07, 2016; 05, 2021

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