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Measurement of the millimeter-wave spectrum of the KO radical, using direct absorption methods, suggests that the ground electronic state is X2Πi with a close-lying excited state approximately 120 cm−1 higher in energy.

The pure rotational spectrum of potassium monoxide (KO) has been recorded using millimeter-wave direct absorption spectroscopy. KO was synthesized by the reaction of potassium vapor, produced in a Broida-type oven, with nitrous oxide. No DC discharge was necessary. Eleven rotational transitions belonging to the 2 Π 3/2 spin-orbit component have been measured and have been fit successfully to a case (c) Hamiltonian. Rotational and lambda-doubling constants for this spin-orbit component have been determined. It has been suggested that the ground electronic state of KO is either 2 Π (as for LiO and NaO) or 2 Σ (as for RbO and CsO), both of which lie close in energy. Recent computational studies favor a 2 Σ ground state. Further measurements of the rotational transitions of the 2 Π 1/2 spin-orbit component and the 2 Σ state are currently in progress, as well as the potassium hyperfine structure.

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Rotational spectra of LiNH 2 and NaNH 2 in their X1 A 1 ground electronic states have been recorded using pulsed-beam Fourier transform spectroscopy in the frequency range 22-58 GHz. These species were synthesized in a DC discharge by the reaction of ammonia and the respective laser-ablated alkali metal, in argon carrier gas. Observed transitions were analyzed with previously-measured millimeter-wave frequencies, improving previous rotational constants and determining the metal electric quadrupole hyperfine parameter, χ aa , for both species. We find that χ aa (Li) = 0.494 and χ aa (Na) = -7.688. We also compare our results to DFT calculations. A Townes-Dailey analysis of the quadrupole constants suggest that the bonding of the -NH 2 ligand to lithium and sodium is comparable.