Photoprotons from Be, C, and O

The photoprotons ejected from thin foils of beryllium, carbon, and polyethylene and from oxygen gas by 25-Mev betatron bremsstrahlung were observed in nuclear emulsions with good resolution. The energy distributions and yields of photoprotons were determined for Be, C, and O. Excitation functions for transitions to the ground states of the residual nuclei have been constructed from the observed photoproton energy distributions of C and O. Structure is observed in the proton energy distributions and hence appears in the corresponding ($\gamma , p$) excitation functions. This structure is in rough agreement with that observed in ($\gamma , n$) reactions in C and O.