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 Effelsberg 100 m
telescope in the circumstellar envelope of the carbon-rich
post-AGB star V1610 Cyg, which is somewhat better known
as CRL 2688, by
Nguyen-Q-Rieu, D. Graham, and V. Bujarrabal,
Ammonia and Cyanotriacetylene in the Envelopes of CRL 2688 and IRC +10216
Astron. Astrophys. 138, L5L8 (1984).
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.
DC7N and (individually) 6 of the 7 13C
isotopomers were detected in the study
Detection of HC5N and HC7N Isotopologues in TMC-1 with the Green Bank Telescope
Mon. Not. R. Astron. Soc. 474, 50685075 (2018); by
A. M. Burkhardt, E. Herbst, S. V. Kalenskii, M. C. McCarthy, A. J. Remijan, and B. A. McGuire.