The rotation-inversion spectra and vibration-rotation interaction in NH2D

An additional 86 lines of the NH₂D rotation-inversion spectrum were measured between 7.5 and 850 GHz. These data and the existing NH₂D and ND₂H data are fitted to a Hamiltonian in which the vibration-rotation interaction is included in the form of an offdiagonal inertial tensor term. For comparison with the symmetric ammonias an oblate basis and a Watson-type reduced “S” set of distortion constants are used. A theory for the interaction term is given which is in excellent agreement with experiment. Structural parameters are derived. The magnitude and relative sign of the two dipole moment components of NH₂D are determined and previously measured nitrogen hyperfine structure for both species is reexamined using improved rotational wavefunctions.