Proton-Proton Scattering at 90° from 28 to 68 Mev

Proton-proton scattering cross sections are measured at 45^∘{} in the laboratory system, from 28 Mev to 68 Mev, with an accuracy of about ±{}1.2%. These measurements fill the energy gap between the work of Cork on the low-energy end, and that of Ramsey et al. at higher energies. In the region of overlap with these experiments there is reasonable agreement. The cross section falls monotonically with increasing energy.