Elastic scattering, transfer reactions, and fission induced byO16ions onTa181andPb208

Abstract

Total cross sections for the quasielastic and fission channels in reactions of $^{16}\mathrm{O}$ on $^{181}\mathrm{Ta}$ and $^{208}\mathrm{Pb}$ were measured as a function of the incident energy near the Coulomb barrier. For $^{208}\mathrm{Pb}$, the fission and quasielastic components account for essentially all of the total reaction cross sections as deduced from the elastic scattering. However, for $^{181}\mathrm{Ta}$, the fission and quasielastic components account for only about 25% of the total cross section as deduced from elastic scattering. The fission fragment angular distributions for $^{208}\mathrm{Pb}$ are analyzed with a simple statistical approach yielding an effective moment of inertia at the saddle point compatible with the liquid-drop-model prediction. Fission excitation functions for $^{181}\mathrm{Ta}$ are described reasonably well by a statistical evaporation code.NUCLEAR REACTIONS Ta($^{16}\mathrm{O}$, $^{16}\mathrm{O}$), ($^{16}\mathrm{O}$, $^{17}\mathrm{O}$), ($^{16}\mathrm{O}$, $^{15}\mathrm{N}$), ($^{16}\mathrm{O}$, C), ($^{16}\mathrm{O}$, $f$), ${E}_{L}=83, 90, 96$ MeV. $^{208}\mathrm{Pb}$($^{16}\mathrm{O}$, $^{16}\mathrm{O}$), ($^{16}\mathrm{O}$, $^{17}\mathrm{O}$), ($^{16}\mathrm{O}$, $^{15}\mathrm{N}$), ($^{16}\mathrm{O}$, C) ${E}_{L}=80, 83, 88, 90, 96, 102$ MeV, measured $\ensuremath{\sigma}(\ensuremath{\theta}, E)$. $\mathrm{Ta}(^{16}\mathrm{O}, f)$ ${E}_{L}=77\ensuremath{-}102$ MeV, measured $\ensuremath{\sigma}(E)$; deduced optical-model parameters, total reaction cross sections; enriched targets.