Molecular-beam studies of Van der Waals complexes of atmospheric interest

The radio-frequency and microwave spectra of the Ar·O₃ and Ar·SO₂ Van der Waals complexes have been analysed with the conventional first-order centrifugal distortion Hamiltonian plus inversion and centrifugal distortion of the inversion frequency. The centrifugal distortion constants were then used to obtain a force field describing the Van der Waals vibrations. This procedure worked quite well for Ar·O₃, generating vibrational properties appropriate for a semi-rigid complex. Ar·SO₂, however, cannot be described by such a harmonic model. Ar·SO₂ has a very isotropic Van der Waals potential where stretching and bending vibrations are strongly coupled. In addition, a qualitative study of many SO₂-containing bimolecular complexes was made. It was possible to categorize these complexes as having strong, moderate or weak interactions.