The HCnO (n ≥ 3) Radicals in the ISM

The HCO radical was detected in the ISM a long time ago. The detection of the HCCO radical, however, was found only fairly recently.
B. A. McGuire, A. M. Burkhardt, C. N. Shingledecker, S. V. Kalenskii, E. Herbst, A. J. Remijan, and M. C. McCarthy
reported on the
Detection of Interstellar HC5O in TMC-1 with the Green Bank Telescope
Astrophys. J. 843, Art. No. L28 (2017).
Two Λ-components of butadiynylformyl, each consisting of two HFS components, of the J = 17/2 – 15/2 transition were detected in emission near 21.945 GHz.
In addition, the hexatriynylformyl radical, HC7O, was tentatively detected through stacking the Λ-components of two transitions, J = 35/2 – 33/2 and 37/2 – 35/2 near 19.204 and 20.302 GHz, respectively. These reports may appear as space oddities, but we shall know more eventually.

M. A. Cordiner, S. B. Charnley, Z. Kisiel, B. A. McGuire, and Y.-J. Kuan
reported on the
Deep K-band Observations of TMC-1 with the Green Bank Telescope: Detection of HC7O, Nondetection of HC11N, and a Search for New Organic Molecules
Astrophys. J. 850, Art. No. 187 (2017).
The Λ-components of two hexatriynylformyl transitions, J = 35/2 – 33/2 near 19.204 GHz (as before) and 33/2 – 31/2 near 18.107 GHz were detected weakly. Stacking of these data together with those from above yielded a reasonable detection.

Contributor(s): H. S. P. Müller; 07, 2017; 12, 2017