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The cyanido radical (cyano is the old nomenclature) is a radical with molecular formula ·CN. The cyanido radical was one of the first detected molecules in the interstellar medium and has helped the field of astrochemistry a great deal. The first discovery was performed with a coude spectrograph which was made famous and credible due to this detection. ·CN has been observed in both diffuse clouds and dense clouds. Usually, CN is detected in regions with hydrogen cyanide, hydrogen isocyanide, and HCHN+ since it is also used In the creation and destruction of these molecules.
The cyano radical is best depicted as a combination of two resonance structures: the structure with the unpaired electron on the carbon is the minor contributor, while the structure with the unpaired electron on the nitrogen (the isocyano radical) is the major contributor. The charge separation in the isocyano radical is similar to that of carbon monoxide.
Formation and destruction of ·CN
- Dissociative Recombination In Diffuse Clouds: HCN+ + e− → ·CN + ·H 
- Photo-Dissociation In Dense Clouds: HCN + hv → ·CN + ·H
- H3+ + ·CN → HCN+ + H2
Detections of ·CN
The coude spectrograph and a 100-inch (2.5 m) telescope were used to observe ·CN's interstellar lines and ultraviolet spectra. Use of the spectrograph proved McKellar's findings to be correct and also made the spectrograph famous. In 1970, ·CN's first rotational transition from J=0 to J=1 was detected In the Orion Nebula and W51. The first detection of ·CN in extragalactic sources were seen toward Sculptor Galaxy (NGC 253), IC 342, and M82 In 1988. These emission lines seen were from N=1 to N=0 and N=2 to N=1. In 1991, the ·CN vibration-rotational bands were observed in a king furnace at the National Solar Observatory using a McMath Fourier-Transform spectrometer. The observed 2 to 0 lines show an extreme hyperfine structure. In 1995, the rotational absorption spectrum of ·CN in the ground state was observed in the 1 THz region, and most of the lines were measured in the range of 560 to 1020 GHz. Four new rotational transitions were measured; N=8 to N=8, J=15/2 to J=17/2 and J=17/2 to J=19/2; N=7 to N=8, J=15/2 to J=17/2 and J=13/2 to J=15/2.
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- McKellar, Andrew (June 1940). "Evidence for the Molecular Origin of Some Hitherto Unidentified Interstellar Lines". Publications of the Astronomical Society of the Pacific. Publications of the Astronomical Society of the Pacific. 52 (307): 187. Bibcode:1940PASP...52..187M. doi:10.1086/125159.
- Walter S., Adams (January 1941). "Some Results with the COUDÉ Spectrograph of the Mount Wilson Observatory". The Astrophysical Journal. Astrophysical Journal. 93: 11. Bibcode:1941ApJ....93...11A. doi:10.1086/144237.
- Henkel, C.; Schilke, P.; Mauersberger, R. (July 1988). "Molecules in external galaxies - The detection of CN, C2H, and HNC, and the tentative detection of HC3N". 201 (1). Astronomy and Astrophysics: L23–L26. Bibcode:1988A&A...201L..23H.
- Jefferts, K. B.; Penzias, A. A.; Wilson, R. W. (August 1970). "Observation of the CN Radical in the Orion Nebula and W51". The Astrophysical Journal. Astrophysical Journal. 161: L87. Bibcode:1970ApJ...161L..87J. doi:10.1086/180576.
- Klisch, E.; Klaus, T.; Belov, S. P.; Winnewisser, G.; Herbst, E. (December 1995). "Laboratory rotational spectrum of CN in the 1 THz region". 304. Astronomy and Astrophysics: L5. Bibcode:1995A&A...304L...5K.