Microwave Resonance in Nitric Oxide: Lambda Doubling and Hyperfine Structure

The microwave spectrum arising from transitions between Zeeman levels in the ${}_{}{}^2{}_{}{}^{}\Pi _{\frac{3}{2}}^{}{}_{}{}^{}$, $J=\frac{3}{2}$ state of nitric oxide is reinvestigated with particular regard to the lambda doubling which is observable for electric-dipole transitions. This doubling is compared with the theory of Karnaugh. The experiments also give a new and improved determination of the nuclear hyperfine coupling constants and of the molecular splittings. The theory of the hyperfine effect is reexamined in detail.