Using the University of Pennsylvania betatron, the energy dependences of the $\gamma -p$ cross sections of C, Al, Co, Ni, and Cb have been measured. The cross-section curves exhibit the resonance character found in $\gamma -n$ reactions. The significant parameters of each of the curves are tabulated. From the data of this paper and the known $\gamma -n$ cross-section data, the sum of neutron and proton integrated cross sections is evaluated for carbon and nickel.

• Received 6 April 1951

DOI:https://doi.org/10.1103/PhysRev.83.370