On the Detection of Pentadiynylidyne, C5H, in Space

The pentadiynylidyne radical in its 2Π1/2 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,
Tentative Detection of the C5H 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 2Π3/2 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,
Detection of the 2Π3/2 State of C5H,
Astron. Astrophys. 167, L5–L7 (1986).

Subsequently, it was also detected toward TMC-1 in one transition with resolved 1H hyperfine splitting as well as λ-doubling:
J. Cernicharo, M. Guélin, and C. M. Walmsley,
Detection of the Hyperfine Structure of the C5H Radical,
Astron. Astrophys. 172, L5–L6 (1987).


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