Perturbation allowed transitions in the infrared spectrum of 14ND3: determination of the K-dependent parameters in the ground state

Accurate values of the K-dependent constants (i )C, (i )DK and (i )HK in the ground state of 14ND3, with i = s, a, have been determined for the first time thanks to the detections of ‘perturbation allowed’ transitions in the ν1, ν2, ν3, ν4 and 2ν4 infrared bands. The rotation–inversion and inversion transitions from the literature, together with 7289 ground state combination differences from the infrared vibration–rotation–inversion transitions have been simultaneously analysed. The adopted rotation– inversion Hamiltonian includes distortion constants up to the eighth power and thek=±3 andk =±6 interaction terms. Precise values of the diagonal constants and of thek=±3 interaction coefficients have been obtained. Accurate values of the ground state term values have been calculated for both s and a levels up to J = 21.