THE MICROWAVE-SPECTRUM AND STRUCTURE OF THE CARBON-DIOXIDE SULFUR-DIOXIDE COMPLEX

The rotational spectra of nine isotopomers of the carbon dioxide-sulph ur dioxide van der Waals complex were observed with a pulsed molecular beam Fourier transform microwave spectrometer. All odd K energy level s were missing in the symmetric isotopic species, but were present in the singly substituted (COO)-O-18-O-16 or (SOO)-O-18-O-16 isotopomers. No inversion splittings were observed in any of the isotopic species. The observed frequencies for each isotopomer were fit to obtain rotat ional and centrifugal distortion constants. Consideration of the momen ts of inertia, selection rules and missing levels indicate that the co mplex has a cross structure with C-2v symmetry. The C-2 axis of SO2 is perpendicular to the C-infinity axis of CO2. The negative end of the SO2 dipole moment points to the carbon atom. The centre of mass distan ce between the two monomers is 3.29(5) Angstrom. The dipole moment is 1.771(2) D. Distributed multipole electrostatic calculations support t he cross structure.