Hexapentaenylidene in its ¹A₁ ground electronic state has been detected with the 70 m DSN antenna in emission in two rotational transitions toward the dark cloud TMC-1 by
W. D. Langer, T. Velusamy, T. B. H. Kuiper, R. Peng, M. C. McCarthy, M. J. Travers, A. Kovács, C. A. Gottlieb, and P. Thaddeus,
First Astronomical Detection of the Cumulene Carbon Chain Molecule H₂C₆ in TMC-1,
Astrophys. J. 480, L63–L66 (1997)
The ortho transitions 7_1,7 – 6_1,6 and 8_1,8 – 7_1,7 near 18.8 and 21.5 GHZ, respectively, were detected. The lighter homolog C₄H₂ is about 25 times more abundant.

The molecule was also detected by
M. Araki, S. Takano, N. Sakai, S. Yamamoto, T. Oyama, N. Kuze, and K. Tsukiyama,
who studied
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).
The three J = 16 – 15 transitions with K_a = 0 and 1 were detected near 43 GHz with the 100 m GBT.

Contributor(s): H. S. P. Müller; 08, 2012; 10, 2017