Neutron-Helium Interaction. II. Angular Distributions and Phase Shifts from 0.2 to 7.0 MeV

Precision relative differential cross sections for the scattering of neutrons from helium were measured at 22 neutron energies between 0.2 and 7.0 MeV. The measurements were made by observing the energy distribution of the recoiling helium nuclei in a high-pressure helium-gas scintillation counter irradiated by monoenergetic neutrons. An analysis of the data was made in terms of phase shifts. The data could be satisfactorily represented without the use of partial waves higher than $l=1\mathrm{}$. The energy dependence of the phase shifts was found to be in good agreement with that predicted by single-level dispersion theory. Proton-helium phase shifts were calculated from the neutron-helium phase shifts and found to be in fair agreement with the existing data. It is shown that a Saxon-Woods potential can accurately represent the scattering of protons and neutrons from helium for energies at least up to 5 and 8 MeV, respectively.