Knowledge Bank

Rotational spectra of O$2$-H$\mathrm{<mrow\; data-mjx-texclass="ORD">35</mrow>}$Cl and O$2$-H$\mathrm{<mrow\; data-mjx-texclass="ORD">37</mrow>}$Cl have been studied from 3.5 to 21 GHz with an FTMW spectrometer in combination with a supersonic beam system. Several series of lines have been observed in the region. One series consists of strong lines with about 3800 MHz interval, starting at the lowest transition, $J$=1-0. Lines of this series have a small Zeeman effect in comparison with other series. All the observed lines have hyperfine structures caused by the quadrupole coupling of Cl and a much smaller magnetic hyperfine coupling of the proton. The molecular structure, results of $ab$ $initio$ calculations, and the rotational and hyperfine constants will be discussed.