Dynamical synthesis of 4He in the scission phase of nuclear fission

TL;DR

This paper uses advanced density functional theory to analyze the final phase of nuclear fission in plutonium-240, revealing that helium-4 nuclei form dynamically in the neck region during scission, explaining ternary fission.

Contribution

It introduces a novel dynamical mechanism for helium-4 synthesis during nuclear fission, linking cluster formation to the scission process using time-dependent density functional theory.

Findings

Helium-4 clusters form during the neck assembly in less than 1 zeptosecond.

The formation of 4He dominates over other light clusters due to its higher binding energy.

Scission occurs between two alpha-like clusters, explaining ternary fission phenomena.

Abstract

In the exothermic process of fission decay, an atomic nucleus splits into two or more independent fragments. Several aspects of nuclear fission are not properly understood, in particular the formation of the neck between the nascent fragments, and the subsequent mechanism of scission into two or more independent fragments. Using an implementation of time-dependent density functional theory, based on a relativistic energy density functional and including pairing correlations, we analyze the final phase of the process of induced fission of $^{240}$Pu, and show that the time-scale of neck formation coincides with the assembly of two $\alpha$-like clusters (less than 1 zs = 10$^{-21}$ s). Because of its much larger binding energy, the dynamical synthesis of 4He in the neck predominates over other light clusters, e.g., $^3$H and $^6$He. At the instant of scission the neck ruptures exactly between the two $\alpha$-like clusters, which separate because of the Coulomb repulsion and are eventually absorbed by the two emerging fragments. The newly proposed mechanism of light charged clusters formation at scission provides a natural explanation of ternary fission.