Elastic Scattering of Protons by Helium at 5.78 Mev

The differential cross section for the scattering of 5.78-Mev protons by helium has been measured with an accuracy of ±2 percent. Scattered protons and recoil alpha particles were detected in Ilford C-2 nuclear track plates, allowing the calculation of cross sections for 26 angles from 16.2° to 154° in the center-of-mass system. The differential cross sections per unit solid angle are given as a function of the center-of-mass scattering angle. The results, analyzed in terms of phase shifts, confirm the large splitting of the inverted $P_{\frac{3}{2}}-P_{\frac{1}{2}}$ doublet in ${\mathrm{Li}}^5$ and indicate the presence of a small negative $D$ wave phase shift.