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.