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
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-C2H5SH 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 CH3SH as well as that of C2H5OH 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
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 CH3SH/C2H5SH and C2H5OH/C2H5SH 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.

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