Yields and Excitation Curves for the High-Energy Photospallation of Cobalt

Yields of several nuclides from the gamma-ray spallation of cobalt have been measured, using bremsstrahlung from the Cornell 300-Mev electron synchrotron. With 309-Mev bremsstrahlung, the yields are of the order of $\frac{1}{200}$ times the ($\gamma , n$) cross section. A general decrease of yield with increasing number of ejected nucleons was found. Excitation curves for some of the reactions were determined from 174 to 309 Mev. The results indicate that the ($\gamma , 2pn$) reaction is caused primarily by photons of energy less than 174 Mev, while the ($\gamma , 2p5n$), ($\gamma , 2p6n$), and ($\gamma , 3p7n$) reaction yields are contributed to by higher energy photons. The average "effective photon" energy is found to increase with increasing number of ejected nucleons.