Free jet rotational spectrum of propylene oxide-krypton and modelling and ab initio calculations for propylene oxide-rare gas dimers

The rotational spectra of propylene oxide-Kr-84 and propylene oxide-Kr-86 have been measured by free jet millimetre-wave absorption spectroscopy. The preferred experimentally derived conformation of the complex is supported by results obtained with a simple distributed polarisability model and by ab initio calculations. The dissociation energy of the complex has been estimated, from the D-J centrifugal distortion constant, to be ca. 3.7 kJ mol(-1), which compares with 3.3 kJ mol(-1) from the model. Modelling and ab initio calculations have also been performed for the related propylene oxide Ne and propylene oxide-Ar complexes, and led to a re-assignment of their absolute energy minima. The results obtained for the three propylene oxide rare gas atom dimers are compared.