Vibration-inversion-rotation spectra of ammonia. A vibration-inversion-rotation Hamiltonian for NH 2D and ND 2H

The model Hamiltonian developed previously for ammonia NH ₃ has been used to study the vibration-inversion-rotation energy levels of the isotopic species of ammonia NH ₂D and ND ₂H. In this model the inversion motion is removed from the vibrational problem by allowing the molecular reference configuration to be a function of the large amplitude motion coordinate. The ground state inversion-rotation energy levels of NH ₂D and ND ₂H have been calculated with the use of the zeroth-order inversion-rotation Hamiltonian, and the calculated transition frequencies have been compared with the experimental data.