2025MNRAS.542.1423G

The phenyl derivative of ketene, phenylketene (C$_6$H$_5$CHCO), can be considered as a candidate to be observed in the Taurus Molecular Cloud TMC-1. However, due to its high reactivity, there has been no microwave spectroscopic research conducted on it, nor has there been any radioastronomical search for it. In order to enable the interstellar search of phenylketene in TMC-1, in this study, its microwave spectrum was characterized in the laboratory. Gas phase phenylketene was generated by pulsed discharge of mixture of ethynylbenzene (C$_6$H$_5$CCH) and O$_2$, and its rotational signatures were measured using a chirped pulse Fourier transform microwave spectrometer. By assigning 90 pure rotational transitions of phenylketene in the 8-16 GHz range, we obtained accurate rotational constants, enabling broader spectral predictions in high frequency range for interstellar exploration. Discharge microwave spectrum of $^{18}$O$_2$ and other oxygen-containing small molecules, in addition to dioxygen, were also measured to validate the discharge products. Subsequently, we searched for phenylketene molecule in TMC-1, but did not detect it. The upper limit to its abundance in this source was derived.