The scattering of protons of from one- to three-Mev energy by helium has been experimentally examined for the existence of resonance scattering analogous to the neutron-helium resonance observed for one-Mev neutrons by Staub and Stephens. If $n-n$ and $p-p$ nuclear forces are equal, such a resonance should occur in $p-\mathrm{H}\mathrm{e}$ scattering for protons of approximately two Mev. The number of protons scattered through 140° were observed as a function of their energy. This number passed through a maximum at two Mev as expected, but the sharpness and height of the maximum were several times less than for the $n-\mathrm{H}\mathrm{e}$ resonance. However, this greater width and lesser intensity can be qualitatively justified. The number of protons scattered through 76° did not show the presence of a resonance scattering as the energy was varied. Observations of the angular distribution of the scattered protons for angles of scattering between 30° and 140° for proton energies of 1.0, 1.5, 2.0, 2.5 and 3.0 Mev, respectively, have been obtained.

• Received 30 April 1941

DOI:https://doi.org/10.1103/PhysRev.60.42