SCATTERING OF ALIGNED MOLECULES - THE POTENTIAL-ENERGY SURFACES FOR THE KR-O-2 AND XE-O-2 SYSTEMS

Total integral cross sections-for scattering of oxygen molecules on kr ypton and xenon atoms were measured in the thermal energy range, as a function of the collision energy and under a controlled alignment of t he rotational angular momentum of the molecules [Aquilanti er nl., Nat ure, 371, 399 (1994)]. Data obtained with a ''hot'' effusive molecular beam, which contains fast rotating and randomly oriented O-2 molecule s, mainly probe the spherical component of the potential energy surfac es. Experiments with supersonic seeded beams, where the oxygen molecul es are cooled at the K = 1 rotational level and selectively aligned [A quilanti et nl., Phys. Rev. Lett. 74, 2929 (1995)], probe the anisotro py of the potential energy surfaces. The analysis of the experimental results, based upon close-coupling exact quantum mechanical calculatio ns of the cross sections, provides an accurate characterization of the interactions at intermediate and large intermolecular distances for t he Kr-O-2 and Xe-O-2 systems. It is found that the most stable configu ration of the two complexes is for perpendicular approach of the rare gas atom, with energies 15.84 for Kr and 17.87 meV for Xe, at intermol ecular distances of 3.72 and 3.87 Angstrom, respectively. An adiabatic approximation and a semiclassical description Shed light on some gene ral features of the collision dynamics of aligned molecules, in partic ular on the observed effects of the interaction anisotropy on the glor y interference phenomenon. (C) 1998 American Institute of Physics. [S0 021-9606(98)00334-1].