Global fittings of 14N15N16O and 15N14N16O vibrational-rotational line positions using the effective Hamiltonian approach

An effective Hamiltonian built up to sixth order in the Amat-Nielsen ordering scheme describing all rovibrational energy levels in the ground electronic state and containing in explicit form all resonance interaction terms due to the approximate relations between harmonic frequencies ω1≈2ω2 and ω3≈4ω2 was applied to model the observed rovibrational line positions (collected from the literature) of 14N15N16O and 15N14N16O isotopologues of nitrous oxide. For 14N15N16O, 124 effective Hamiltonian parameters were fitted to near 28 000 observed line positions covering the 0.8-8860 cm−1 spectral range. The RMS of the weighted fit is 0.00126 cm−1 and dimensionless standard deviation is 1.48. For 15N14N16O, 121 effective Hamiltonian parameters were fitted to more than 31 000 observed line positions covering the same spectral interval. The RMS of the weighted fit is 0.00185 cm−1 and dimensionless standard deviation is 1.85. In both cases the models describe all available line positions with precision compatible to the measurement uncertainties. A number of local resonance perturbations was found and discussed. Among these perturbations there are interpolyad resonance Coriolis interactions. A comparison of HITRAN-2008 data with the calculations based on the fitted models is presented.