THE ANISOTROPIC INTERACTION OF HE-C2H2 FROM DIFFERENTIAL SCATTERING EXPERIMENTS

The anisotropic potential energy surface of He-C2H2 is determined by a nalyzing total differential cross sections measured- at E = 71.3- meV and differential energy loss spectra obtained at two energies, E = 102 .9 and 62.0 meV. Calculations are carried out using infinite-order-sud den, coupled states, and close coupling methods. The data evaluation c learly demonstrates that the experimental results are much better repr oduced by a spindle-shaped contour in the repulsive potential than by the more usual hard ellipsoidal shape. This change also explains the u nusually small damping of the diffraction oscillations in the total di fferential cross section.