Measurement of the Fission Thresholds ofPu239,U233,U235, andU238Using the (d, p) Reaction

摘要: An experiment is described which measures the fission thresholds of thermally fissionable nuclides. In contrast to induced by neutron capture, use ($d, p$) reaction allows compound nuclei be produced with excitations less than binding energy last neutron. Measurements spectra protons in coincidence fission, normalized all emitted protons, have allowed ${\mathrm{Pu}}^{239}$, ${\mathrm{U}}^{233}$, and ${\mathrm{U}}^{235}$ observed. It should emphasized that nucleus stable against emission region these thresholds, thus avoiding distortions this competing reaction. The threshold ${\mathrm{U}}^{238}$ was also obtained for comparison data. case even-even nuclei, observed step structure a clear indication multiple barrier. This barrier predicted collective model correlated experimental equivalent energies at center first are as follows: -1.61 Mev; -1.47 ${\mathrm{U}}^{235}$, -0.60 Mev. second observable only two: -0.72 Mev, agrees well data from excitation. each probability decreases positive energies. would result either if were compete or there significant contribution proton spectrum electric breakup deuteron.