| Résumé | The van der Waals complex NH3-CO has been studied in the infrared and millimetre wave regions, and analysed on the basis of the distinction between the ortho- and para -NH3 nuclear spin species. The spectrum and energy level pattern of ortho -NH3-CO are relatively simple, closely resembling those of the Ne-CO and Ar-CO complexes. The situation for para -NH3- CO is somewhat more complicated, with observed states having K values which differ by �1 from that of the analogous ortho -NH3-CO state. This indicates that the lowest energy orientation of para -NH3 in the complex lies in a Pi configuration. The present results correlate very well with the only previous study of NH3-CO, in the microwave region, and clarify the nature of the rotational series observed there. The infrared band centre of NH3-CO is only very slightly shifted (<0.2 cm-1) from that of the free CO molecule, indicating that the CO vibration has little effect on the intermolecular forces. |
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