===== 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,\\
**[[https://ui.adsabs.harvard.edu/abs/1985ApJ...295..501B|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,\\
**[[https://ui.adsabs.harvard.edu/abs/1995ApJ...441..334S|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,\\
**[[https://ui.adsabs.harvard.edu/abs/1995ApJ...445..325F|Vibrationally Excited H<sub>2</sub>, HCl, and NO<sup>+</sup> 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,\\
**[[https://doi.org/10.1086/309570|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.,\\
**[[https://doi.org/10.1051/0004-6361/201014553|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<sup>–1</sup> 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,\\
**[[https://doi.org/10.1051/0004-6361/201322225|Fundamental Vibrational Transitions of Hydrogen Chloride Detected in CRL 2136]]**\\
//Astron. Astrophys.// **558**, Art. No. L5 (2013).


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


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