Modeling barrier-top fission dynamics in a discrete-basis formalism

TL;DR

This paper introduces a configuration-interaction model for fission barrier dynamics, emphasizing the role of pairing and diabatic interactions, and highlights differences from traditional transition-state theory.

Contribution

It develops a novel discrete-basis formalism for modeling barrier-top fission dynamics using self-consistent mean-field configurations.

Findings

Pairing and diabatic interactions significantly influence fission-to-capture ratios.

The model shows insensitivity of the branching ratio to pre-scission decay widths.

Barrier-top dynamics involve distributed transport over many configurations.

Abstract

A configuration-interaction model is presented for the barrier region of induced fission. The configuration space is composed of seniority-zero configurations constructed from self-consistent mean-field wave functions. The Hamiltonian matrix elements between configurations include diabatic and pairing interactions between particles. Other aspects of the Hamiltonian are treated statistically, guided by phenomenological input of compound-nucleus transmission coefficients. In this exploratory study the configuration space is restricted to neutron excitations only. A key observable calculated in the model is the fission-to-capture branching ratio. We find that both pairing and diabatic interactions are important for achieving large branching to the fission channels. In accordance with the transition-state theory of fission, the calculated branching ratio is found to be quite insensitive to the fission decay widths of the pre-scission configurations. However, the barrier-top dynamics appear to be quite different from transition-state theory in that the transport is distributed over many excited configurations at the barrier top.