Knowledge Bank

Rotational spectra of \textit{trans}-, \textit{cis}-HOCO and DOCO have been observed using an Fourier transform microwave(FTMW) spectrometer and the FTMW-mmw-DR technique. The \textit{cis}-conformer was observed for the first time in the gas phase. The HOCO radical was produced in a supersonic jet by discharging a gas mixture of CO and H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O diluted in Ar. The molecular constants including the hyperfine coupling constants have been precisely determined. The determined $r0$ structure of the two conformers are consistent with those of \textit{ab initio} calculations. The fermi constants of the two conformers indicate that the spin densities on the hydrogen nuclei are different between the two conformers.