===== On the Detection of Hexapentaenylidene, C6H2, in Space =====

Hexapentaenylidene in its <sup>1</sup>A<sub>1</sub> 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,\\
**[[https://doi.org/10.1086/310622|First Astronomical Detection of the Cumulene Carbon Chain Molecule H<sub>2</sub>C<sub>6</sub> in TMC-1]]**,\\
//Astrophys. J.// **480**, L63–L66 (1997)\\
The //ortho// transitions 7<sub>1,7</sub> – 6<sub>1,6</sub> and 8<sub>1,8</sub> – 7<sub>1,7</sub> near 18.8 and 21.5 GHZ, respectively, were detected. The lighter homolog C<sub>4</sub>H<sub>2</sub> 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\\
**[[https://doi.org/10.3847/1538-4357/aa8637|Long Carbon Chains in the Warm Carbon-chain-chemistry Source L1527: First Detection of C<sub>7</sub>H in Molecular Clouds]]**,\\
//Astrophys. J.// **847** Art. No. 51 (2017).\\
The three //J// = 16 – 15 transitions with //K<sub>a</sub>// = 0 and 1 were detected near 43 GHz with the 100 m GBT.


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

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