Knowledge Bank

We have previously reported the microwave spectrum of the mono-fluoromethyl radical, $CH2F$, and have discussed its planarity in the ground vibronic $state1$. In the present study the microwave spectrum of its chlorine analogue, $CH2Cl$, was observed for the first time. Molecular constants including the fine and hyperfine structure constants have been determined precisely for both the $\mathrm{<mrow\; data-mjx-texclass="ORD">35</mrow>}Cl$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">37</mrow>}Cl$ species. Contrary to the case of $CH2F$ for which the equilibrium configuration seems to be slightly nonplanar, the $CH2Cl$ radical is planar judging from its small positive inertial defect. The CCl bond length determined was quite short and comparable to that of HCCl.