Knowledge Bank

The rotational spectra of the NaO radical in the four lowest vibrational states were observed in millimeter and sub-millimeter wave region. The NaO radical was generated by the reaction of sodium vapor with $N2O$ in a heat pipe cell. Analysis of the observed spectra yielded the rotational and centrifugal distortion constants, $\Lambda$-type doubling constants, spin-orbit interaction constant, and hyperfine interaction constants in the four vibrational states. The NaO radical is clearly shown to have a $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\pi i$ ground electronic state with an anomalously large $\Lambda$-type doubling constant and very small hyperfine interaction constants. The molecular constants derived will be discussed in terms of the ionic character of the bond.