Molecular Parameters of OH Free Radical

Theoretical formulas with higher-order perturbation terms are given for the rotational levels of ${}_{}{}^2{}_{}{}^{}\mathrm{II}$ states, and are applied to the OH free radical. By analyzing existing data values of several molecular parameters including the rotational constant $B$, the spin-orbit coupling constant $A$ and $\Lambda$-doublet constants $\alpha$ and $\beta$ are obtained for some vibrational states. The magnetic $g$ factors are discussed and analyzed. A recent experiment on laser magnetic reasonance (LMR) is also discussed.