# Deformed shell effects in $^{48}$Ca+$^{249}$Bk quasifission fragments

## TL;DR

This study uses time-dependent Hartree-Fock calculations to explore how shell effects, especially octupole deformed shell gaps at N=56, influence quasifission fragment formation in $^{48}$Ca+$^{249}$Bk collisions, revealing new insights into superheavy element synthesis.

## Contribution

It demonstrates the impact of octupole shell effects on quasifission, contrasting with previous focus on doubly-magic nuclei, and suggests experimental ways to identify these effects.

## Key findings

- Shell effects similar to fission influence quasifission fragments.
- Octupole shell gap at N=56 affects central collisions.
- Mass-angle correlations can isolate N=56 influenced fragments.

## Abstract

Background: Quasifission is the main reaction channel hindering the formation of superheavy nuclei (SHN). Its understanding will help to optimize entrance channels for SHN studies. Quasifission also provides a probe to understand the influence of shell effects in the formation of the fragments. Purpose: Investigate the role of shell effects in quasifission and their interplay with the orientation of the deformed target in the entrance channel. Methods: $^{48}$Ca$+^{249}$Bk collisions are studied with the time-dependent Hartree-Fock approach for a range of angular momenta and orientations. Results: Unlike similar reactions with a $^{238}$U target, no significant shell effects which could be attributed to $^{208}$Pb "doubly-magic" nucleus are found. However, the octupole deformed shell gap at $N=56$ seems to strongly influence quasifission in the most central collisions. Conclusions: Shell effects similar to those observed in fission affect the formation of quasifission fragments. Mass-angle correlations could be used to experimentally isolate the fragments influenced by $N=56$ octupole shell gaps.