Further evidence for energy sorting from the even-odd effect in fission-fragment element distributions

TL;DR

This paper provides evidence that the even-odd effect in nuclear fission fragment distributions is driven by an energy-sorting process, where entropy influences the distribution of excitation energy and unpaired nucleons.

Contribution

It introduces a statistical mechanics model explaining the even-odd effect as a signature of energy sorting in fission, linking entropy to fragment excitation energy distribution.

Findings

The even-odd effect varies with fissioning nucleus mass.

Asymmetric splits show increased even-odd effect.

The model supports energy sorting as a key mechanism.

Abstract

The even-odd effect in fission is explained by a model based on statistical mechanics. It reveals that the variation of the even-odd effect with the mass of the fissioning nucleus and the increase towards asymmetric splits is due to the important statistical weight of configurations where the light fission fragment populates the ground state of an even-even nucleus. This implies that entropy drives excitation energy and unpaired nucleons predominantly to the heavy fragment. Therefore, the even-odd effect is an additional signature of the recently discovered energy-sorting process in fission.