Rotational spectrum, structure and modeling of the SO2 – CS2 complex

The rotational spectra of seven isotopomers of the SO2–CS2 van der Waals dimer have been observed with a Fourier transform microwave spectrometer. The rotational constants for the normal species were determined to be A52413.2000(3) MHz, B51105.3803(3) MHz and C 5884.9885(2) MHz. They are consistent with the SO2 straddling the CS2 molecule and Cs symmetry for the complex. The centers of mass of the two monomers are separated by 3.4287~2! Å. Two structures were found that are consistent with this symmetry which differ in the relative tilt of the CS2 and SO2 . In both structures, the C2 axis of the SO2 is aligned close to parallel to the CS2 molecular axis with the oxygen end of the SO2 tipped closer to the CS2 . In one structure the deviation from parallel is 9.8~8!° while in the other it is 17.7~11!°. The dipole moment components have been determined to be ma50.0137(5) D and mb51.1961(9) D. A semi-empirical model employing electrostatic, dispersion and repulsion interactions was employed to analyze the system and resulted in a reasonable reproduction of the angular geometry. A comparison of the results for the SO2–CS2 complex with the closely related SO2–CO2 and SO2–OCS complexes is presented. © 1999 American Institute of Physics. @S0021-9606~99!00314-1#