# Effect of shell structure on the fission of sub-lead nuclei

## TL;DR

This study investigates the role of shell effects in the asymmetric fission of sub-lead nuclei, using microscopic calculations to demonstrate the universality of the underlying mechanisms across different nuclear regions.

## Contribution

It introduces a new method to analyze shell effects at scission and confirms that similar mechanisms drive asymmetric fission in both actinides and sub-lead nuclei.

## Key findings

- Shell effects influence fragment mass asymmetry in sub-lead fission.
- Mechanisms for asymmetric fission are consistent across actinides and sub-lead regions.
- Proposed method effectively identifies dominant shell effects at scission.

## Abstract

Fission of atomic nuclei often produces mass asymmetric fragments. However, the origin of this asymmetry was believed to be different in actinides and in the sub-lead region [A. Andreyev {\it et al.}, Phys. Rev. Lett. {\bf 105}, 252502 (2010)]. It has recently been argued that quantum shell effects stabilising pear shapes of the fission fragments could explain the observed asymmetries in fission of actinides[G. Scamps and C. Simenel, Nature {\bf 564}, 382 (2018)]. This interpretation is tested in the sub-lead region using microscopic mean-field calculations of fission based on the Hartree-Fock approach with BCS pairing correlations. The evolution of the number of protons and neutrons in asymmetric fragments of mercury isotope fissions is interpreted in terms of deformed shell gaps in the fragments. A new method is proposed to investigate the dominant shell effects in the pre-fragments at scission. We conclude that the mechanisms responsible for asymmetric fissions in the sub-lead region are the same as in the actinide region, which is a strong indication of their universality.