The ground state of KO revisited: the millimeter and submillimeter spectrum of potassium oxide

摘要

The millimeter/sub-millimeter spectrum of the KO radical has been recorded in the frequency range 90-534 GHz using direct absorption methods. The radical was synthesized by reacting potassium vapor, produced with a Broida-type oven, with either N2O or O-2 mixed in argon carrier gas. Twenty-seven rotational transitions of KO were measured, each exhibiting a doublet structure with a relatively small splitting (similar to 100-200 MHz) that increased noticeably with frequency. A perturbation was apparent in the rotational lines at energies above similar to 120 cm(-1), which was more prominent in one doublet component. The data were successfully fit with a Hund's case (c) Hamiltonian, assuming that spectra arise from a (2)pi(i) state, and rotational and effective lambda-doubling constants were determined. Higher order centrifugal distortion terms were needed to account for the perturbation. The spectra could also be fit as a (2)sigma(+) ground state, but less successfully, and the resulting rotational constant of B = 8235.4 MHz disagreed significantly with that predicted by theory. On the basis of the experimental data, the ground electronic state of KO has been assigned as (2)pi(i), although the (2)sigma(+) assignment cannot be entirely ruled out.