Absolute differential cross sections for the production of photoprotons from carbon, lithium, and beryllium have been measured using the Oxford 110-Mev synchrotron. A proton telescope was used to select protons of energy 37 Mev, 47 Mev, 55 Mev, 63 Mev, and 78 Mev, using bremsstrahlung beams with peak energies from 40 Mev to 110 Mev. Measurements were taken at angles of 36°, 51°, 71°, 90°, 119°, and 129°. Comparison of the carbon results with the calculations of Dedrick indicate that the principal contributions to the cross sections arise from quasi-deuteron interactions. Some evidence is presented that other processes occur near threshold. Measurements of neutron-proton coincidences were made showing that this direct manifestation of the quasi-deuteron interaction occurs at these energies.

• Received 31 January 1958

DOI:https://doi.org/10.1103/PhysRev.110.941