===== On the Detection of Amidogen, NH2, in the Interstellar Medium =====

The //N<sub>KaKc</sub>// = 1<sub>10</sub> – 1<sub>01</sub> //para// rotational transition of amidogen, NH<sub>2</sub>, was observed in absorption toward Sgr B2 (N) and (M):\\
E. F. van Dishoek, D. J. Jansen, P. Schilke, and T. G. Philips,\\
**[[https://doi.org/10.1086/187076|Discovery of the Interstellar NH<sub>2</sub> Radical]]**\\
//Astrophys. J.// **416**, L83–L86 (1993).\\
Three fine structure components were observed with partially resolved <sup>14</sup>N hyperfine structure which obviously secures the identification.\\
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Further transitions were reported in\\
J. R. Goicoechea, N. J. Rodríguez-Fernández and J. Cernicharo,\\
**[[https://doi.org/10.1086/379704|The Far-Infrared Spectrum of the Sagittarius B2 Region: Extended Molecular Absorption, Photodissociation, and Photoionization]]**\\
//Astrophys. J.// **600**, 214–233 (2004).\\
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 M. Melosso, L. Bizzocchi, O. Sipilä, B. M. Giuliano, L. Dore, F. Tamassia, M.-A. Martin-Drumel, O. Pirali, E. Redaelli, and P. Caselli\\
reported on the\\
**[[https://doi.org/10.1051/0004-6361/202038490|First detection of NHD and ND2 in the interstellar medium — Amidogen deuteration in IRAS 16293–2422]]**\\
//Astron. Astrophys.// **641**, Art. No. A153 (2020).\\
Both isotopologs were detected in archival HIFI///Herschel// data taken toward the Class 0 protostar IRAS 16293−2422. Very high degrees of deuteration were inferred.\\
\\

A similar account was given shortly thereafter by\\
A. Bacmann, A. Faure, P. Hily-Blant, K. Kobayashi, H. Ozeki, S. Yamamoto, L. Pagani, and F. Lique,\\
**[[https://doi.org/10.1093/mnras/staa2903|Deuterium fractionation of nitrogen hydrides: detections of NHD and ND2]]**\\
//Mon. Not. R. Astron. Soc.// **499**, 1795 (2020).\\
NHD observations are based on archival APEX data, ND<sub>2</sub> observations on archival HIFI///Herschel// data as above. The numbers are very similar to the ones above. One can deduce deuteration degrees per A atom of ~0.25 and ~0.35 for NHD and ND<sub>2</sub>, respectively, from their total column densities.\\
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Contributor(s): H. S. P. Müller; 03, 2007; 02, 2023

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