===== On the Detection of Pentadiynylidyne, C5H, in Space =====

The pentadiynylidyne radical in its <sup>2</sup>Π<sub>1/2</sub> lower spin component has been detected in six lines of three rotational transitions toward IRC +10216 by\\
J. Cernicharo, C. Kahane, J. Gómez-González; and M. Guélin,\\
**[[https://ui.adsabs.harvard.edu/abs/1986A%26A...164L...1C|Tentative Detection of the C<sub>5</sub>H Radical]]**,\\
//Astron. Astrophys.// **164**, L1–L4 (1986)\\
before it was actually detected in the laboratory.

Confirmation came also through the observation of four lines pertaining to the <sup>2</sup>Π<sub>3/2</sub> upper spin component in the 3 mm range for which the //λ//-doubling is just not resolvable:\\
J. Cernicharo, C. Kahane, J. Gómez-González; and M. Guélin,\\
**[[https://ui.adsabs.harvard.edu/abs/1986A%26A...167L...5C|Detection of the <sup>2</sup>Π<sub>3/2</sub> State of C<sub>5</sub>H]]**,\\
//Astron. Astrophys.// **167**, L5–L7 (1986).

Subsequently, it was also detected toward TMC-1 in one transition with resolved <sup>1</sup>H hyperfine splitting as well as //λ//-doubling:\\
J. Cernicharo, M. Guélin, and C. M. Walmsley,\\
**[[https://ui.adsabs.harvard.edu/abs/1987A%26A...172L...5C|Detection of the Hyperfine Structure of the C<sub>5</sub>H Radical]]**,\\
//Astron. Astrophys.// **172**, L5–L6 (1987).


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Contributor(s): H. S. P. Müller; 05, 2007

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