A determination of fundamental Zeeman parameters for the OH radical

Abstract

Measurements of the gas-phase E.P.R. spectra of OH in the J = 9/2 and 11/2 levels of the X²II state at 26 GHz and 35 GHz respectively are reported. Confocal and semi-confocal optical resonators have been used in place of the more conventional microwave cavities for these experiments. The data are analysed, together with previous measurements by Radford on other rotational levels in the determination of six independent g factors:

These parameters are interpreted in terms of the electronic structure of the OH radical. In agreement with previous workers, it is found that the major contaminant of the X²II state is the A²Σ⁺ state and that this pair of states is a good example of Van Vleck's pure precession hypothesis.