A. Fuente, J. R. Goicoechea, J. Pety, R. Le Gal, R. Martín-Doménech, P. Gratier, V. Guzmán, E. Roueff, J. C. Loison, G. M. Muñoz Caro, V. Wakelam, M. Gerin, P. Riviere-Marichalar, and T. Vidal,
reported on the
First Detection of Interstellar S₂H,
Astrophys. J. 851 L49 (2017).
The 6_0,6 – 5_0,5 and 7_0,7 – 6_0,6 transitions near 94.6 and 110.4 GHz were detected with the IRAM 30 m telescope in emission toward the Horsehead photodissociation region. The large fine structure splitting was resolved, the very small HFS splitting was not resolved. The radical occurs widespread in this source, both in the interface region (HCO peak) and in the denser and colder region (DCO⁺ peak). Its column density is only a factor of about four to six lower in this source than that of H₂S.

More recently, G. Esplugues, M. Agúndez, G. Molpeceres, B. Tercero, C. Cabezas, N. Marcelino, R. Fuentetaja, and J. Cernicharo
announced the
First Detection of HS₂ in a Cold Dark Cloud,
Astron. Astrophys. 699 L2 (2025).
As usual, the authors rersorted to the QUIJOTE molecular line survey of TMC-1 carried out with the Yebes 40 m dish and covering 31.0 to 50.4 GHz. HS₂ is about 7 times more abundant than HSO in TMC-1.

Contributor(s): H. S. P. Müller; 12, 2017; 07, 2025