Relative Photofission Yields of Several Fissionable Materials

Relative photofission yields of U²³⁸, U²³⁶, U²³⁵, U²³⁴, U²³³, Th²³², Np²³⁷, and Pu²³⁹ were measured at three betatron energies with a photomultiplier fission fragment detector. Results at betatron energies of 17 and 20 Mev are in agreement and give the following relative fission values: Th²³², 0.31; U²³⁸, 1.00; U²³⁶, 1.43; U²³⁵, 2.40; U²³⁴, 1.82; U²³³, 2.54; Np²³⁷, 2.40; Pu²³⁹, 3.17. The relative (γ, f) yields are empirically correlated with the nuclear parameter Z²A. Some comments are made on the competition between fission and neutron emission.