Isobaric yield distribution in the fission of uranium by medium-energy protons

Abstract

The independent formation cross sections of 139Ba, 139Ce, 141Ce, and 143Ce, and the cumulative formation cross sections of 139Cs, 141Ba, and 143La, produced from the fission of natural uranium by protons of energies 20–85 MeV, have been measured radiochemically. The proton energies at which the excitation functions reach their maxima correlate well with the neutron-to-proton ratio of the fission product. Nuclear charge-dispersion curves exhibit, with increasing proton energy, the behavior previously found by other workers, i.e. broadening and a shift of the most probable nuclear charge towards stability.