The 1,3-pentadiyne molecule CH3C4H, aka methyldiacetylene,
had been identified in spectra recorded toward TMC-1 by
two groups independently and at almost the same time
J. M. MacLeod, L. W. Avery, N. W. Broten,
The detection of interstellar methyldiacetylene (CH3C4H)
Astrophys. J. 282, L89L92 (1984);
C. M. Walmsley, P. R. Jewell, L. E. Snyder, and G. Winnewisser,
Detection of interstellar methyldiacetylene (CH3C4H) in the dark dust cloud TMC 1
Astron. Astrophys. 184, L11L14 (1984).
The molecule was also detected by
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).
The three J = 11 10 transitions with K = 0, 1, and 2 were detected near 44.8 GHz with the 100 m GBT.