The ketenyl radical is almost linear with the Ka = 1 levels being so high in energy that for astronomical observations it can be treated as being linear.
M. Agúndez, J. Cernicharo, and M. Guélin
reported on the
Discovery of Interstellar Ketenyl (HCCO), a Surprisingly Abundant Radical
Astron. Astrophys. 577, Art. No. L5 (2015).
The IRAM 30 m telescope was used to detect the four ΔF = ΔJ = ΔN hyperfine components with N = 4 – 3 near 86.65 GHz toward the dense core Lupus-1A, which is in the vicinity of the low-mass protostar IRAS 15398-3359, and toward the the young stellar object IRAS 18148–0440 in the L483 dense core.
Contributor(s): H. S. P. Müller; 05, 2015