Abstract: The yields of U²³⁷ and a fission product were measured as a function of maximum betatron energy, The ratio of the number of fissions divided by the number of U²³⁷ atoms increases with increasing maximum betatron energy. This is consistent with the picture that the higher-energy gammas leave the U²³⁷ atoms with enough excitation energy (above photofission and photoneutron thresholds) to also decay by fission or neutron emission. This secondary process increases the number of fissions and decreases the U²³⁷ yield, this increasing the above ratio.