Coriolis and l-type interactions in the ν2, 2ν2, and ν4 states of 14NH3

Abstract High-resolution infrared spectra have been remeasured for the ν 2 , 2 ν 2 , and ν 4 bands of 4 NH 3 using a vacuum grating infrared spectrometer and a diode laser spectrometer. Far-infrared spectra of 14 NH 3 have been measured with microwave accuracy in the 700–1100 GHz region by employing a submillimeter wave spectrometer (RAD) with acoustic detection. The pure inversion and inversion-rotation transition frequencies in the ν 2 excited state of 14 NH 3 have been determined for the first time. The vibration-inversion-rotation Hamiltonian of ammonia [Spirko, Stone, and Papousek, J. Mol. Spectrosc. 60 , 159–178 (1976)] has been used for a precise parameterization of the energy levels of ammonia. The ground state rotational and centrifugal constants of 14 NH 3 have been determined using a modified method of combination differences. Coriolis and l -type interactions between ν 2 , ν 4 , 2 ν 2 , ν 2 + ν 4 , and 3 ν 2 states have been analyzed and the band parameters have been obtained which reproduce the transition frequencies within the accuracy of the experimental data.