Formation and dynamics of fission fragments

TLDR

Although nuclear fission occurs on a long time‑scale, rapid shape evolution near scission challenges the adiabatic assumption that internal degrees of freedom are equilibrated along the fission path. The study examines symmetric fission of ^258,264Fm using time‑dependent Hartree‑Fock starting from an adiabatic configuration, and analyzes post‑scission vibrational modes of the fragments. The dynamics significantly affect the kinetic and excitation energies of the fragments.

Abstract

Although the overall time-scale for nuclear fission is long, suggesting a slow process, rapid shape evolution occurs in its later stages near scission. Theoretical prediction of the fission fragments and their characteristics are often based on the assumption that the internal degrees of freedom are equilibrated along the fission path. However, this adiabatic approximation may break down near scission. This is studied for the symmetric fission of $^{258,264}$Fm. The non-adiabatic evolution is computed using the time-dependent Hartree-Fock method, starting from an adiabatic configuration where the fragments have acquired their identity. It is shown that dynamics has an important effect on the kinetic and excitation energies of the fragments. The vibrational modes of the fragments in the post-scission evolution are also analyzed.