On the Detection of the Butadiynyl Radical, C4H, in Extragalactic Sources

S. Muller, A. Beelen, M. Guélin, S. Aalto, J. H. Black, F. Combes, S. J. Curran, P. Theule, and S. N. Longmore
used the Australia Telescope Compact Array (ATCA) to study the molecular content of a foreground galaxy at z = 0.89 (FG0.89 consisting of two subsources, FG0.89SW and FG0.89NO) in absorption toward the quasar PKS 1830-211:
Molecules at z = 0.89: A 4-mm-Rest-Frame Absorption-Line Survey toward PKS 1830-211
Astron. Astrophys. 535, (2011) Art. No. A103.
The linear butadiynyl radical, C4H, was identified by its N = 6 – 5 to 9 – 8 transitions with rest frequencies between 57.0 and 85.7 GHz. All transitions display fine structure splitting of about 40 MHz, whereas the H-hyperfine structure was not resolved. Even though the signal-to-noise ratio appears to be fairly good, it may be the cause of some relative intensity issue in the fine structure components of a respective rotational transition.

Contributor(s): H. S. P. Müller; 5, 2012