On Hydrogen Chloride, HCl, in Space

The J = 1 – 0 transition of HCl was detected in emission with the KAO:
G. A. Blake, J Keene, and T. G. Phillips,
Chlorine in Dense Interstellar Clouds – The Abundance of HCl in OMC-1
Astrophys. J. 295, 501–506 (1985).
More recently, this transition was mapped with the CSO:
P. Schilke, T. G. Phillips, and N. Wang,
Hydrogen Chloride in OMC-1
Astrophys. J. 441, 334–342 (1995).

The Hubble Space Telescope has been used to detect HCl in the diffuse medium toward ζ Oph via its UV spectrum by:
S. R. Federman, J. A. Cardell, E. F. van Dishoek, D. L. Lambert, and J. H. Black,
Vibrationally Excited H2, HCl, and NO+ in the Diffuse Clouds toward ζ Ophiuchi
Astrophys. J. 445, 325–329 (1995).

HCl was also seen with the KAO in absorption toward Sgr B2, just as HF soon thereafter:
J. Zmuidzinas, G. A. Blake, J. Carlsstrom, J. Keene, and D. Miller,
HCl Absorption Toward Sagittarius B2
Astrophys. J. 447, L125–L128 (1995).

The molecule is also present in the circumstellar envelope of the carbon rich star CW Leo:
J. Cernicharo, L. Decin, M. J. Barlow, et al.,
Detection of Anhydrous Hydrochloric Acid, HCl, in IRC +10216 with the Herschel SPIRE and PACS spectrometers
Astron. Astrophys. 518, Art. No. L136 (2010).

Several rovibrational transitions of HCl around 2850 cm–1 or 3.5 μm were detected in absorption with CRIRES at the Very Large Telescope and, more extensively, with IRCS at the Subaru Telescope toward CRL 2136 by:
M. Goto, T. Usuda, T. R. Geballe, K. M. Menten, N. Indriolo, and D. A. Neufeld,
Fundamental Vibrational Transitions of Hydrogen Chloride Detected in CRL 2136
Astron. Astrophys. 558, Art. No. L5 (2013).

Contributor(s): H. S. P. Müller; 03, 2007; 08, 2011; 11, 2013