===== On the Detection of Cyanodiacetylene, HC5N, in the ISM ===== L. W. Avery, N. W. Broten, J. M. McLeod, T. Oka, and H. W. Kroto\\ reported on the\\ **[[https://ui.adsabs.harvard.edu/abs/1976ApJ...205L.173A|Detection of the Heavy Interstellar Molecule Cyanodiacetylene]]**\\ //Astrophys. J.// **205**, L173–L175 (1976).\\ The //J// = 4 – 3 transition near 10.651 GHz was observed in emission toward Sagittarius (Sgr) B2 employing the 46 m radio telecope of the Algonquin Radio Observatory. N. W. Broten, J. M. McLeod, T. Oka, L. W. Avery, J. W. Brooks, R. X. McGee, and L. M. Newton\\ reported subsequently on\\ **[[https://ui.adsabs.harvard.edu/abs/1976ApJ...209L.143B|Evidence for Weak Maser Action in Interstellar Cyanodiacetylene]]**\\ //Astrophys. J.// **209**, L143–L147 (1976).\\ The //J// = 8 – 7 transition near 21.301 GHz was observed toward Sagittarius /Sgr) B2 employing the 46 m radio telecope of the Algonquin Radio Observatory. In addition, the Parkes 64 m dish was used to study the The //J// = 1 – 0 transition near 2.663 GHz with well-resolved hyperfine structure. The high intensity of the latter emission lines were viewed as evidence for weak maser activity. L. T. Little, P. W. Riley, and D. N. Matheson\\ reported on the\\ **[[https://doi.org/10.1093/mnras/181.1.33P|Detection of the //J// = 9 → 8 Transition of Interstellar Cyanodiacetylene]]**\\ //Mon. Not. R. Astron. Soc.// **181**, 33P–35P (1977).\\ TMC-1 was observed with the 25 m dish of the Chilbolton Observatory. The authors mention an earlier report by J. M. MacLeod et al. at an IAU meeting. More recently, the Effelsberg 100 m telecope was used to study the circumstellar shell of the famous carbon star CW Leo:\\ G. Winnewisser and C. M. Walmsley,\\ **[[https://ui.adsabs.harvard.edu/abs/1978A%26A....70L..37W|The Detection of HC5N and HC7N in IRC +10216]]**\\ //Astron. Astrophys.// **70**, L37–L39 (1978).\\ The //J// = 9 – 8 transition near 23.964 GHz was detected for the smaller polyyne.\\ As HC3N and HC7N earlier, HC5N has also been detected in protoplanetary nebulae such as CRL 2688, CRL 618 in 1988 and others later. The detection of DC5N in TMC-1 was reported by two groups simultaneously:\\ J. M. MacLeod, L. W. Avery, and N. W. Broten,\\ **[[https://ui.adsabs.harvard.edu/abs/1981ApJ...251L..33M|//Astrophys. J.//]] 251**, L33–L36 (1981); and\\ F. P. Schloerb, R. L. Snell, W. D. Langer, and J. S. Young,\\ **[[http://cdsads.u-strasbg.fr/abs/1981ApJ...251L..37S|//Astrophys. J.//]] 251**, L37–L41 (1981).\\ The inferred D/H ratio is slightly higher than 0.01. S. Takano, H. Suzuki, M. Ohishi, S.-I. Ishikawa, N. Kaifu, Y. Hirahara, and A. Masuda\\ used the Nobeyama 45 m telescope for the\\ **[[https://ui.adsabs.harvard.edu/abs/1990ApJ...361L..15T|Detection of Five 13C Isotopic Species of HC5N in TMC-1]]**\\ //Astrophys. J.// **361**, L15–L18 (1990).\\ The //J// = 14 – 13 transitions bewteen 36 and 38 GHz were detected at intensities compatible with the 12C/13C ratio in the solar neighborhood. K. Taniguchi and M. Saito\\ reported on the\\ **[[https://doi.org/10.1093/pasj/psx065|First Detection of HC515N in the Interstellar Medium]]**\\ //Publ. Astron. Soc. Japan// **69**, Art. No. L7 (2017).\\ The Nobeyama 45 m telescope was used to detect the //J// = 9 – 8 transition near 23.375 GHz. The 14N/15N ratio derived via the 13C isotopomers is 344±53, slightly lower than 440 in the local ISM. In the case of HC3N, they determined a ratio of 257±54. Vibrationally excited molecules have been detected with the IRAM 30 m telescope in the circumstellar envelope of the carbon-rich post-AGB star V353 Aur, which is somewhat better known as CRL 618, by\\ J. R. Pardo, J. Cernicharo, and J. R. Goicoechea,\\ **[[https://doi.org/10.1086/430774|Observational Evidence of the Formation of Cyanopolyynes in CRL 618 through the Polymerization of HCN]]**\\ //Astrophys. J.// **628**, 275–282 (2005).\\ Four low-lying states (//v//11 = 1 to 3 and //v//10 = 1) were detected with vibrational energies of up to about 315 cm–1. ---- Contributor(s): H. S. P. Müller; 01, 2018. ----