POTENTIAL-ENERGY SURFACES FOR UNSATURATED-HYDROCARBONS FROM CROSSED MOLECULAR-BEAMS

The total differential scattering cross sections for several important unsaturated hydrocarbon molecules with common atmospheric gases were measured in a crossed molecular beam apparatus. The experiments show q uantum interferences which relate to potential energy surface paramete rs, such as the well depth and radial minimum. The damping of the quan tum features, over contributions from experimental resolutions, provid es information on the angular and radial anisotropies present in the p otential energy surfaces. We have investigated two areas: (1) the role of the probe partner in determining the interaction strength for a gi ven hydrocarbon target, and (2) the effect of increasing the overall l ength of the hydrocarbon molecule for a fixed probe. By comparing resu lts for a class of scattering systems, we can identify chemical and ph ysical trends that determine the van der Waals potential energy surfac es of larger molecules. We expect these results to aid in the predicti on and interpretation of complementary experimental measurements on th e high resolution infrared spectroscopy of weakly bound complexes.