Probing postsaddle nuclear dissipation with excitation energy at scission

Abstract

Using the stochastic Langevin model coupled with a statistical decay model, we study postsaddle dissipation properties in fission by analyzing the excitation energy at scission (${E}_{\mathrm{sc}}^{*}$) measured in fissioning nuclei $^{179}\mathrm{Re}$ and $^{254,256}\mathrm{Fm}$. The postsaddle dissipation strength ($\ensuremath{\beta}$) required to fit ${E}_{\mathrm{sc}}^{*}$ data is found to be larger for $^{254,256}\mathrm{Fm}$ than light $^{179}\mathrm{Re}$ which has a smaller postsaddle deformation compared to heavy $^{254,256}\mathrm{Fm}$, showing a rise of nuclear dissipation strength at a greater deformation. Furthermore, we explore the influence of initial excitation energy of a fissioning system $^{246}\mathrm{Cf}$ on the sensitivity of its ${E}_{\mathrm{sc}}^{*}$ to $\ensuremath{\beta}$, and find that the sensitivity is significantly enhanced with increasing the initial excitation energy. Our finding suggests that, on the experimental side, to more accurately probe the postsaddle dissipation strength through the measurement of ${E}_{\mathrm{sc}}^{*}$, it is best to yield those fissioning systems with high energy.