The heptatriynylidyne radical in its 2Πr state
has been detected with the IRAM 30 M telescope in five lines of
three rotational transitions toward the nearby C-rich AGB star CW Leonis by
M. Guélin, J. Cernicharo, M. J. Travers, M. C. McCarthy, C. A. Gottlieb, P. Thaddeus, M. Ohishi, S. Saito, and S. Yamamoto,
Detection of a new Linear Carbon Chain Radical: C7H,
Astron. Astrophys. 317 L1L4 (1997).
The J = 47.5 46.5, 48.5 47.5, and half of the 49.5 48.5 were detected betwen 83.0 and 86.6 GHz.
M. Araki, S. Takano, N. Sakai, S. Yamamoto, T. Oyama, N. Kuze, and K. Tsukiyama
Long Carbon Chains in the Warm Carbon-chain-chemistry Source L1527: First Detection of C7H in Molecular Clouds,
Astrophys. J. 847 Art. No. 51 (2017).
Using the 100 m GBT, four Λ-components of the two transitions with J = 24.5 23.5 and 25.5 24.5 near 42.85 and 44.60 GHz were detected barely to reasonably well; a composite spectrum is beyond doubt.