Fission cross sections of heavy nuclei as a probe of nuclear dissipation

Abstract

Nuclear fission is hindered by dissipation. Using the stochastic Langevin model, we calculate the drop of fission cross sections caused by friction with respect to its standard statistical-model values, ${\ensuremath{\sigma}}_{f}^{\mathrm{drop}}$, as a function of the presadde dissipation strength $(\ensuremath{\beta})$ for $^{226}\mathrm{U}$, $^{234}\mathrm{U}$, and $^{242}\mathrm{U}$. It is shown that the sensitivity of ${\ensuremath{\sigma}}_{f}^{\mathrm{drop}}$ to $\ensuremath{\beta}$ is substantially enhanced with increasing the isospin of the U fissioning system. Furthermore, we find that under typical conditions of excitation energy and angular momentum populating $^{240}\mathrm{U}$ (via radioactive beams) and $^{200}\mathrm{Tl}$ (via stable beams), the fission cross section of the high-isospin heavy $^{240}\mathrm{U}$ demonstrates a greater sensitivity to friction than that of the light $^{200}\mathrm{Tl}$. Our findings suggest that on the experimental side, to accurately probe presaddle dissipation with fission cross sections of heavy nuclei, it is useful to choose radioactive nuclear beams induced reactions as a way to populate excited heavy fissioning systems with high isospin.