Previously reported evidence for photofission of iron is investigated by a more extensive study. Thin foils of iron were bombarded with beams of 1.5-, 3-, 5-, and 16-GeV electrons. $\gamma$-ray spectroscopy and radiochemical measurements were used to measure yields of radionuclides produced in the targets. The yields of 25 nuclides were measured for the bombarded iron foils; these include eight nuclides in the mass region $22<~A<~35$. A thin aluminum target was bombarded with 16-GeV electrons, and the yields of seven radionuclides were measured. The yield of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Na}$ in a thick iron target was measured as a function of target thickness and compared with that of radionuclides produced by cascade-evaporation reactions. The experimental evidence obtained in this series of experiments indicates that nuclides of mass <35 produced in the iron targets are the result of a fissionlike process. For cascade-evaporation reaction products, there is a decrease in the variation of yield with $\Delta Z$ as the bremsstrahlung energy is increased.

• Received 22 June 1970

DOI:https://doi.org/10.1103/PhysRevC.2.1371