190 MeV proton-induced symmetric and asymmetric fission

Abstract

Proton-induced fission (${E}_{\mathrm{p}}=190$ MeV) has been studied for uranium and selected nuclei, $140\ensuremath{\lesssim}A\ensuremath{\lesssim}200$. Analysis of coincident-fragment energies suggests highly asymmetric fission near $A=140$, even in the presence of relatively high fission barriers. The data have been compared with statistical-model fission calculations modified to include precompound nucleon emission. The data can be reproduced using standard fission-barrier and level-density parameters.NUCLEAR REACTIONS Fission, $^{\mathrm{nat}}\mathrm{U}$, $^{197}\mathrm{Au}$, $^{169}\mathrm{Tm}$, $^{159}\mathrm{Tb}$, $^{\mathrm{nat}}\mathrm{Ce}(\mathrm{p}, f)$. $E=190$ MeV; measured ${\ensuremath{\sigma}}_{f}$ (90\ifmmode^\circ\else\textdegree\fi{}), angular correlations, coincident fragment energies. Deduced mass division, total kinetic energy release, fission cross sections; compared with statistical-model fission calculations.