THE INTERMOLECULAR POTENTIAL OF AR-ACETYLENE - INFORMATION FROM INFRARED AND MICROWAVE SPECTROSCOPY

The intermolecular potential of Ar-HCCH is modelled using an atom-atom pairwise-additive approximation, including anisotropic Ar-C repulsions. Close-coupling calculations of the van der Waals bending, stretching and rotational states are carried out. Three potentials that reproduce the experimental rotational energy levels of the vibrational ground state are obtained, and predictions of the excited van der Waals vibrational states supported by these potentials are made. The pattern of energy levels shows that the excited bending states are best described by free-internal-rotor quantum numbers. Measurements of spectra involving excited bending states would distinguish between the three potentials and would provide important new information on the potential energy surface.