Low-Energy Repulsive Interaction Potential for Helium

Abstract

New measurements of the integral elastic cross section for a ⁴He velocity selected supersonic molecular beam scattered by a ⁴He gas target at 2°K are reported. The structure in the velocity dependent cross section arising from the quantum statistics is well resolved and gives precise information about the weakly repulsive potential at values corresponding to the collision energies (5–30 meV). It is shown that the measured property is insensitive to both the attractive and strongly repulsive parts of the potential. The error in the determination of the potential due to the uncertainty of the velocity selector calibration is discussed. A comparison of the présent data with predictions from recently proposed helium potentials is made, and information on the weakly repulsive interaction obtained from this and other experimental data is summarized.