Symmetry of Neutron-InducedU235Fission at Individual Resonances. II

Abstract

Neutrons from the Project Gnome nuclear test were resolved in energy by time-of-flight and used to study symmetry of fission in ${\mathrm{U}}^{235}$ in the resonance region. Symmetry was deduced by measurement of the fission product ratio ${\mathrm{Ag}}^{111}$/${\mathrm{Mo}}^{99}$ at resonances from 8.8 to 40 eV. The maximum decrease observed in the probability of symmetric fission as compared to the probability in thermal fission of ${\mathrm{U}}^{235}$ was 50%. The maximum increase observed was 22%. Four levels showed an increase in symmetry. Thirteen levels showed a decrease in symmetry. With the exception of one level at 15.4 eV, assignments of levels by symmetry are in agreement, in the region covered, with previous work.