Fission Fragment Mass and Kinetic Energy Yields of Fermium Isotopes

TL;DR

This paper presents a comprehensive model of the fission process in heavy nuclei, accurately predicting fragment yields and energies, and analyzing the transition from asymmetric to symmetric fission in fermium isotopes.

Contribution

It introduces a 4D Fourier shape parametrization combined with Langevin dynamics to model fission, incorporating charge equilibration and neutron evaporation effects.

Findings

Model reproduces experimental fission fragment distributions

Identifies transition from asymmetric to symmetric fission in fermium isotopes

Provides detailed correlations between fission observables

Abstract

A rapidly converging 4-dimensional Fourier shape parametrization is used to model the fission process of heavy nuclei. Potential energy landscapes are computed within the macroscopic-microscopic approach, on top of which the multi-dimensional Langevin equation is solved to describe the fission dynamics. Charge equilibration at scission and de-excitation by neutron evaporation of the primary fragments after scission is investigated. The model describes various observables, including fission-fragment mass, charge, and kinetic energy yields, as well as post-scission neutron multiplicities and, most importantly, their correlations, which are crucial to unravel the complexity of the fission process. The parameters of the dynamical model were tuned to reproduce experimental data obtained from thermal neutron-induced fission of $^{235}$U, which allows us to discuss the transition from asymmetric to symmetric fission along the Fm isotopic chain.