Angular Distributions of Photoprotons

The angular distributions of photoprotons from Cu, Ni, and Co targets irradiated with bremsstrahlung of 23-Mev maximum energy have been measured. Protons from Cu and Co show a large asymmetric component which is described by the expression ${(sin\theta +0.5\mathrm{}sin\theta cos\theta )}^2$. Absorption experiments on the protons are consistent with the assignment of the asymmetric component to transitions involving discrete levels in the vicinity of the ground state of the residual nucleus. The angular distributions observed are interpreted as resulting from interference between electric dipole and quadrupole absorption of the initial photons with the relative quadrupole intensity equal to 5 percent.