Detection of the NaO radical by microwave spectroscopy

The rotational spectrum of the NaO radical in the four lowest vibrational states was observed in the millimeter- and submillimeter-wave region. The NaO radical was generated by the reaction of the sodium vapor with N2O directly in a high-temperature absorption cell. Analysis of the observed spectra yielded the rotational and centrifugal distortion constants, Λ-type doubling constants, spin–orbit interaction constants, and hyperfine interaction constants in the four vibrational states. The NaO radical is clearly shown to have the 2Πi ground electronic state with an anomalously large Λ-type doubling constant and very small hyperfine interaction constants. The molecular constants derived are discussed in terms of the ionic character of the bond.