Fourier-over-spheroid shape parametrization applied to nuclear fission dynamics
K. Pomorski, B. Nerlo-Pomorska, C. Schmitt, Zhigang Xiao, Yong-Jing Chen, L. L. Liu
Abstract
We propose a new, rapidly convergent shape parametrization, the so-called Fourier-over-spheroid (FoS) approach, to model fission of heavy nuclei. Four collective coordinates are used to characterize the shape of the fissioning system: its elongation, left-right asymmetry, neck size, and nonaxiality. The potential energy landscape is computed within the macroscopic-microscopic approach, on the top of which the multidimensional Langevin equation is solved to describe the dynamics. Charge equilibration at scission and deexcitation of the primary fragments after scission are further considered. The model gives access to a wide variety of observables, including fission fragments' mass, charge, and kinetic energy yields, fragment mean $N/Z$ and postscission neutron multiplicities, and, importantly, their correlations. The latter are crucial to unravel the complexity of the fission process. The parameters of the model were tuned to reproduce experimental observation from thermal neutron-induced fission of $^{235}\mathrm{U}$, and next used to discuss the transition from the asymmetric to symmetric fission along the Fm isotopic chain.