Fission fragments intrinsic spins and their correlations

TL;DR

This paper introduces a microscopic theoretical framework to analyze the intrinsic spins and their correlations in fission fragments, providing new insights and first-time calculations for specific uranium isotopes.

Contribution

It develops a fully microscopic real-time density functional theory approach to extract intrinsic spin distributions and correlations in fission fragments, a first in the field.

Findings

First microscopic extraction of spin distributions for $^{236}$U and $^{240}$Pu.

Discovery of new qualitative features in spin correlations.

Provides a basis for understanding fragment de-excitation mechanisms.

Abstract

The intrinsic spins and their correlations are the least understood characteristics of fission fragments from both theoretical and experimental points of view. In many nuclear reactions the emerging fragments are typically excited and acquire an intrinsic excitation energy and an intrinsic spin depending on the type of the reactions and interaction mechanism. Both the intrinsic excitation energies and the fragments intrinsic spins and parities are controlled by the interaction mechanism and conservations laws, which lead to their correlations and determines the character of their de-excitation mechanism. We outline here a framework for the theoretical extraction of the intrinsic spin distributions of the fragments and their correlations within the fully microscopic real-time density functional theory formalism and illustrate it on the example of induced fission of $^{236}$U and $^{240}$Pu, using two nuclear energy density functionals. These fission fragment intrinsic spin distributions display new qualitative features previously not discussed in literature. Within this fully microscopic framework we extract for the first time the intrinsic spin distributions of fission fragments of $^{236}$U and $^{240}$Pu as well as the correlations of their intrinsic spins, which have been debated in literature for more than six decades with no definite conclusions so far.