Microwave optical double resonance of NH₂. VI. Ground state of NHD

Microwave optical double resonance studies of the ground vibronic state of NHD have been carried out. Both a-type rotational transitions between K doublet levels and magnetic dipole transitions between fine structure components have been observed. Analysis of the hyperfine structure completes the determination of the hyperfine coupling tensor for the proton. It is found that one of the principal axes of the tensor nearly coincides with the NH bond direction and that this magnetic dipole coupling tensor is reasonably consistent with the odd electron being in a p orbital on the N atom perpendicular to the molecular plane. The MODR observations have been combined with ground state combination differences from previous optical studies to give improved rotational and fine structure constants. It also has been possible to determine the magnitude of the off-diagonal component of the spin-rotation tensor, ε_ab, as 1.07±0.09 GHz, from the mixing of states differing by 1 in K_a.