H. W. Kroto, C. Kirby, D. R. M. Walton, L. W. Avery, N. W. Broten,
J. M. MacLeod, and T. Oka,
The Detection of Cyanohexatriyne, H(C≡C)3CN, in Heile's Cloud 2
Astrophys. J. 219, L133L137 (1978)
reported the first detection of this cyanopolyyne in two transitions (J = 9 8 and 21 20 near 10.15 and 23.69 GHz, respectively) in Heile's Cloud 2 employing the 46 m radio telecope of the Algonquin Radio Observatory.
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,
The Detection of HC5N and HC7N in IRC +10216
Astron. Astrophys. 70, L37L39 (1978).
The J = 21 10 transition near 23.688 GHz was detected for the larger polyyne.
The molecule has also 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,
Observational Evidence of the Formation of Cyanopolyynes in CRL 618 through the Polymerization of HCN
Astrophys. J. 628, 275282 (2005).
G. Langston and B. E. Turner described the
Detection of 13C Isotopomers of the Molecule HC7N
Astrophys. J. 658, 455461 (2007).
They searched for the J = 12 11 and 13 12 transitions in TMC-1 using the GBT 100 m telescope. No individual isotopomer was found. Instead, a barely significant signal was obtained by averaging all observations.