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

Comments: 12 pages, 9 figures