MICROWAVE SPECTRA OF THE BUTADIENE-$SO_{2}$ COMPLEX

The microwave spectrum of the butadiene-$SO_{2}$ complex has been observed using a pulsed beam, Fourier transform microwave spectrometer. Twenty-nine a-, b- and c- dipole transitions have been fitted with a Watson S-reduced Hamiltonian. The rotational constants thus determined are A=2793.889 MHz, B=1325.436 MHz and C=1123.053 MHz. The complex has no plane of symmetry. The butadiene and $SO_{2}$ planes are stacked with $SO_{2}$ sitting approximately above the mid-point of the butadiene molecule. The distance between the two subunits is about 3.2 \\AA. Isotope experiments to better understand the structure of the complex will be described.