Fragment Kinetic Energy Release in Heavy-Ion-Induced Fission Reactions

Abstract

The most probable kinetic-energy release in fission reactions induced by 125-MeV ${\mathrm{C}}^{12}$ ions and 166-MeV ${\mathrm{O}}^{16}$ ions has been measured for the target nuclei ${\mathrm{Pr}}^{141}$, ${\mathrm{Tb}}^{159}$, ${\mathrm{Ho}}^{165}$, ${\mathrm{Tm}}^{169}$, ${\mathrm{Lu}}^{175}$, ${\mathrm{Au}}^{197}$, ${\mathrm{Bi}}^{209}$, ${\mathrm{Th}}^{232}$, ${\mathrm{U}}^{238}$, and ${\mathrm{Pu}}^{240}$. Silicon diode surface-barrier detectors were used in these measurements, and a ${\mathrm{Cf}}^{252}$ spontaneous-fission source served as the absolute energy standard. A least-squares analysis of our data and those obtained by others gives ${\overline{E}}_K\left(\mathrm{MeV}\right)=0.1065\mathrm{} \frac{Z^2}{A^{\frac{1}{3}}}+20.1\mathrm{}$. The dependence of the most probable kinetic energy on the scission shape of the fissioning nucleus has been examined by comparison with recent calculations based on the work of Cohen and Swiatecki. The data are consistent with scission shapes corresponding to spheroids whose shapes minimize the total energy of the system.