MOLECULAR CONSTANTS OF NITROUS OXIDE 14N216O

The zero-order frequencies, anharmonic and vibration-rotation coupling constants up to fourth order have been calculated for the molecule of nitrous oxide, 14N216O, from a careful analysis of all available experimental data on the vibration-rotation energy levels of the molecule. It was found inevitable to include the fourth-order constants in the energy expression in order to reproduce the recent accurate measurements to within their experimental uncertainties. A thorough study has been made of the various anharmonic interactions influencing the energy levels. To obtain a stable solution for the molecular constants in a least-squares adjustment to the observed energy levels involved in these interactions, it was found necessary to treat the vibrational (J = 0) and vibrational-rotational (J > 0) terms simultaneously; a general procedure effecting this calculation is described in detail. With the inclusion of the Fermi interaction connected with matrix elements of the type 〈v1v2lv3J∥v1-1v2+2 lv3J〉 the observed levels up to 5700 cm-1 could be reproduced with a standard deviation of 0.006 cm-1. On the other hand, to attain a satisfactory fit also for the high levels observed in the photographic infrared region (8700 to 12000 cm-1), additional interactions of the type 〈v1v2lv3 | v1-2 v2l v3+1〉 had to be taken into account. However, the values obtained for the constants respousible for these interactions are not considered entirely satisfactory due to the somewhat inferior accuracy of the available photographic infrared data. © 1968.