Fission Dynamics of Compound Nuclei: Pairing versus Fluctuations

TL;DR

This study uses a time-dependent Hartree-Fock+BCS approach to analyze fission dynamics in $^{240}$Pu, revealing how temperature and fluctuations influence fission pathways and observables, aligning with experimental data.

Contribution

It introduces a microscopic model incorporating thermal fluctuations to explain fission fragment distributions and energies, supporting the Brosa model with detailed dynamical insights.

Findings

Fission evolution time increases at finite temperature.

Dynamical pairing diminishes at high excitations, requiring fluctuations.

Two main fission channels (S1 and S2) explain experimental results.

Abstract

Energy dependence of fission observables is a key issue for wide nuclear applications. We studied real-time fission dynamics from low-energy to high excitations in the compound nucleus $^{240}$Pu with the time-dependent Hartree-Fock+BCS approach. It is shown that the evolution time of the later phase of fission towards scission is considerably lengthened at finite temperature. As the role of dynamical pairing is vanishing at high excitations, the random transition between single-particle levels around the Fermi surface to mimic thermal fluctuations is indispensable to drive fission. The obtained fission yields and total kinetic energies with fluctuations can be divided into two asymmetric scission channels, namely S1 and S2, which explain well experimental results, and give microscopic support to the Brosa model. With increasing fluctuations, S2 channel takes over S1 channel and the spreading fission observables are obtained.