Deformed shell effects in Ca 48 + Bk 249 quasifission fragments

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: Ca48+Bk249 collisions are studied with the time-dependent Hartree-Fock approach for a range of angular momenta and orientations. Results: Unlike similar reactions with a U238 target, no significant shell effects which could be attributed to the Pb208 "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.