Anatomy of neck configuration in fission decay

TL;DR

This study investigates the microscopic structure of neck configurations in the fission decay of Uranium and Thorium isotopes, revealing neutron-rich necks and potential new fission modes relevant to stellar nucleosynthesis.

Contribution

It provides a detailed microscopic analysis of neck configurations in various isotopes, highlighting the role of neutron-rich necks and their impact on fission decay modes.

Findings

Neutron component in necks increases with isotope mass number.

Maximum neutron-proton ratio around 5 in certain isotopes.

Possible indication of new fission decay modes like multi-fragmentation.

Abstract

The anatomy of neck configuration in the fission decay of Uranium and Thorium isotopes is investigated in a microscopic study using Relativistic mean field theory. The study includes $^{236}U$ and $^{232}Th$ in the valley of stability and exotic neutron rich isotopes $^{250}U$, $^{256}U$, $^{260}U$, $^{240}Th$, $^{250}Th$, $^{256}Th$ likely to play important role in the r-process nucleosynthesis in stellar evolution. Following the static fission path, the neck configurations are generated and their composition in terms of the number of neutrons and protons are obtained showing the progressive rise in the neutron component with the increase of mass number. Strong correlation between the neutron multiplicity in the fission decay and the number of neutrons in the neck is seen. The maximum neutron-proton ratio is about 5 for $^{260}$U and $^{256}$Th suggestive of the break down of liquid-drop picture and inhibition of the fission decay in still heavier isotopes. Neck as precursor of a new mode of fission decay like multi-fragmentation fission may also be inferred from this study.