Intermolecular Potentials from Crossed Beam Differential Elastic Scattering Measurements. III. He+He and Ne+Ne

High‐resolution differential cross sections for elastic scattering extending to wide scattering angles for $\mathrm{He}–\mathrm{He}$ and $\mathrm{Ne}–\mathrm{Ne}$ have been measured at two collision energies in the thermal range. The experiments were carried out by crossing two supersonic nozzle atom beams at right angles and detecting the atoms scattered in the plane of the beams with a rotatable electron‐bombardment mass‐filter universal detector. The results are analyzed to yield information on the interatomic potentials for these systems using a realistic and flexible potential function, and comparison is made with previously proposed potentials. For He₂, a somewhat ``harder'' low‐energy repulsion than that of most such potentials is inferred, while for Ne₂ the potential well depth found is $\text{∼ 30 \%}$ larger than earlier estimates and in good agreement with a preliminary spectroscopic finding.