===== Detection of Hydrogen Sulfide, H2S, in the ISM ===== Hydrogen sulfide has been detected in seven star-forming regions very early as a very abundant molecule via its 110 – 101 transition in the 2 mm region:\\ P. Thaddeus, M. L. Kutner, A. A. Penzias, R. W. Wilson, and K. B. Jefferts,\\ **[[https://ui.adsabs.harvard.edu/abs/1972ApJ...176L..73T|Interstellar Hydrogen Sulfide]]**\\ //Astrophys. J.// **176**, L73–L76 (1972).\\ H2S was also identified in this transition toward the circumstellar envelope of OH231.8+4.2:\\ N. Ukita, M. Morris,\\ **[[https://ui.adsabs.harvard.edu/abs/1983A%26A...121...15U|Hydrogen Sulfide in a Circumstellar Envelope]]**\\ //Astron Astrophys.// **121**, 15–18 (1983);\\ and also in certain regions of the cold dark clouds L134N and TMC-1:\\ Y. C. Minh, W. M. Irvine, and L. M. Ziurys,\\ **[[https://doi.org/10.1086/185553|Detection of Interstellar Hydrogen Sulfide in Cold, Dark Clouds]]**\\ //Astrophys. J.// **345**, L63–L66 (1989). The same transition was used to identify H234S toward certain regions in the Orion molecular cloud:\\ Y. C. Minh, W. M. Irvine, D. McGonagle, and L. M. Ziurys,\\ **[[https://doi.org/10.1086/169103|Observations of the H2S toward OMC-1]]**\\ //Astrophys. J.// **360**, 136–141 (1990). A weak feature near 333 GHz has been identified as the 202 – 111 of HDS:\\ G. H. Macdonald, A. G. Gibb, R. J. Habing, and T. J. Millar,\\ **[[https://doi.org/10.1051/aas:1996249|A 330–360 GHz Spectral Survey of G 34.3+0.15. I. Data and Physical Analysis]]**\\ //Astron Astrophys. Suppl. Ser.// **119**, 333–367 (1996). Even D2S was recently detected toward two dense, cold clouds Barnard 1 and NGC 1333 IRAS 4A(DCO+), with HDS detected toward several additional sources:\\ C. Vastel, T. G. Phillips, C. Ceccarelli, and J. C. Pearson,\\ **[[https://doi.org/10.1086/378261|First Detection of Doubly Deuterated Hydrogen Sulfide]]**\\ //Astrophys. J.// **593**, L97–L100 (2003). HD34S was identified in\\ **[[https://doi.org/10.1093/mnras/sty462|The ALMA-PILS Survey: The Sulfur Connection between Protostars and Comets: IRAS 16293–2422 B and 67P/Churyumov-Gerasimenko]]**\\ //Mon. Not. R. Astron. Soc.// **476**, 4949–4964 (2018) by\\ M. N. Drozdovskaya, E. F. van Dishoeck, J. K. Jørgensen, U. Calmonte, M. H. D. van der Wiel, A. Coutens, H. Calcutt, H. S. P. Müller, P. Bjerkeli, M. V. Persson, S. F. Wampfler, and K. Altwegg.\\ Only the 202 – 111 transition was detected clearly for HD34S and HDS at 332255 and 333279 MHz, respectively. Other lines in the survey were too weak to be detected, as expected. An important detail is that the ratio of approximately 20 is close to the terrestrial value. ---- Contributor(s): H. S. P. Müller; 10, 2008; 08, 2018 ----