Ethenone, H2CCO, aka ketene, had been identified first in spectra recorded toward Sgr B2(OH) by
B. E. Turner,
Microwave Detection of Interstellar Ketene
Astrophys. J. 213, L75–L79 (1977).
The NRAO 11 m telecope was employed to identify three Ka = 1 transitions with J' = 4 and 5. The fourth transition and the two Ka = 0 transitions were detected tentatively around 81 and 101 GHz.

Evidence for the J' = 4, Ka = 0 and 1 transitions were found in Orion A by:
L. E. B. Johansson, C. Andersson, J. Eldér, P. Friberg, Å. Hjalmarson, B. Höglund, W. M. Irvine, H. Olofsson, and G. Rydbeck,
Spectral Scan of Orion A and IRC +10216 from 72 to 91 GHz
Astron. Astrophys. 130, 227–256 (1984).

It is also fairly abundant in dark clouds:
M. Ohishi, K. Kawaguchi, N. Kaifu, W. M. Irvine, Y. C. Minh, S. Yamamoto, S. Saito,
The Ortho to Para Ratio for Ketene in TMC-1
ASP Conf. Ser. 16, 387–391 (1991).

It was also found in three translucent clouds (CB 17 CB 24, and CB 228):
B. E. Turner, R. Terzieva, and E. Herbst,
The Physics and Chemistry of Small Translucent Molecular Clouds. XII. More Complex Species Explainable by Gas-Phase Processes
Astrophys. J. 518, 699–732 (1999).

J. K. Jørgensen, H. S. P. Müller, H. Calcutt, A. Coutens, M. N. Drozdovskaya, K. I. Öberg, M. V. Persson, V. Taquet, E. F. van Dishoeck, and S. F. Wampfler
reported on
The ALMA-PILS Survey: Isotopic Composition of Oxygen-containing Complex Organic Molecules toward IRAS 16293–2422B
Astron. Astrophys. 620, Art. No. A170 (2018).
The results were obtained in the course of a line survey of the solar-type protostellar binary IRAS 16293–2422 with ALMA covering the frequency range 329.1–362.9 GHz. The authors only investigated source B. They detected for the first time both 13C isotopomers as well as the mono-deuterated isotopolog. The D/H ratio per H atom is about 0.02 (the HDCCO/H2CCO ratio is about 0.04). Many lines of the main isotopic species were optically thick; the local ISM 12C/13C ratio of 68 was assumed. The 18O and the doubly deuterated isotopologs were near the detection limit and not identified with certainty. Ketene is among the molecules with colder rotational temperatures of around 125 K in that hot corino.

Contributor(s): H. S. P. Müller; 06, 2006; 03, 2012; 01, 2019

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