Atomic-Beam Scattering Studies on the Li–Hg System: Quantum Effects and Velocity Dependence of the Cross Sections

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Abstract
Measurements of the velocity dependence of the angular intensity distribution of 6Li and 7Li beams scattered by a crossed Hg beam are reported. The Li beams were velocity selected, the Hg beam Maxwellian. Angular intensity distributions were measured at various relative velocities (vr) from 700–1200 m/sec, relative total cross sections (q) from vr=300 to 1350 m/sec. The differential cross sections show expected quantum interferences. Scattering patterns for 6Li— and 7Li–Hg are found to be identical at the same de Broglie wavelength. The over‐all angular dependence of the scattering at low angles follows the θ−7/3 relationship characteristic of an r−6 long‐range potential. Extrema in the total cross sections q(vr) were also observed. The experimental data were analyzed in terms of a Lennard‐Jones (12, 6) potential, but it was not possible to determine a unique set of potential parameters. Comparison of observed and calculated results has yielded three nearly equivalent sets of σ, ε lying within the ranges 2.5≤σ≤3.5 Å, 480°≤ε/k≤1000°K.