Absolute total cross sections for Li-molecule scattering

Abstract

Absolute total scattering cross sections were measured for 7Li scattered by D2, N2, CO, CO2, CH4, and SF6 over a range of Li beam velocities of 0.75–4.75 × 105 cm/sec corresponding to a range of relative kinetic energies of 0.04–0.33 eV for Li–D2 to 0.02–0.79 eV for Li–SF6. In the observed cross sections random experimental errors were less than 1.5% and systematic errors were between −0.3% and +1.4%. Two spherically symmetric potentials, the Lennard-Jones (12,6) and the Buckingham-Corner were fit to deconvoluted and statistically smoothed data using a non-linear least squares fitting routine. For each Li-molecule system a satisfactory fit could be obtained with standard deviations of approximately 1%–2%. The best fit potentials gave accurate values for the average long range attractive part of the potentials over the range of limiting impact parameters. Evidence from high resolution differential cross section experiments is introduced that indicates that there should be relatively little damping of the glory features of the total scattering cross sections for the Li-molecule systems studied here, and hence the ability of spherical potentials to reproduce the data is not surprising.