Structure, properties, and inversion of the Ar⋅SO2 van der Waals molecule

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Abstract
Microwave and radiofrequency spectra of the Ar⋅SO2 van der Waals molecule have been studied by molecular beam spectroscopy. The molecule has C s point group symmetry and tunnels through a very low barrier at a C 2v structure at a 980 MHz rate. The tunneling interchanges the two oxygen atoms which causes half of each inversion doublet to have zero statistical weight. The inversion frequency and assumptions about the bending vibration lead to a barrier height of ?10 cm−1. Stark effectmeasurements give μ a =0.2674 D, μ b =0.0 D, μ c =1.465 D. These moments are interpreted in terms of a vibrational amplitude of 24° associated with the inversion coordinate. The geometry of the complex is essentially perpendicular with the Ar atom above the plane of SO2 and located almost directly over the SO2 center‐of‐mass at a 3.675 Å distance.