Fusion and quasifission dynamics in the reactionsCa48+Bk249and

Abstract

Background: Synthesis of superheavy elements (SHE) with fusion-evaporation reactions is strongly hindered by the quasifission (QF) mechanism which prevents the formation of an equilibrated compound nucleus and which depends on the structure of the reactants. New SHE have been recently produced with doubly-magic 48 Ca beams. However, SHE synthesis experiments with single-magic 50 Ti beams have so far been unsuccessful.Purpose: In connection with experimental searches for Z = 117, 119 superheavy elements, we perform a theoretical study of fusion and quasifission mechanisms in 48 Ca, 50 Ti + 249 Bk reactions in order to investigate possible differences in reaction mechanisms induced by these two projectiles.Methods: The collision dynamics and the outcome of the reactions are studied using unrestricted time-dependent Hartree-Fock (TDHF) calculations as well as the density-constrained TDHF method to extract the nucleus-nucleus potentials and the excitation energy in each fragment.Results: Nucleus-nucleus potentials, nuclear contact times, masses and charges of the fragments, as well as their kinetic and excitation energies strongly depend on the orientation of the prolate 249 Bk nucleus. Long contact times associated with fusion are observed in collisions of both projectiles with the side of the 249 Bk nucleus, but not on collisions with its tip. The energy and impact parameter dependencies of the fragment properties, as well as their mass-angle and mass-total kinetic energy correlations are investigated.Conclusions: Entrance channel reaction dynamics are similar with both 48 Ca and 50 Ti projectiles. Both are expected to lead to the formation of a compound nucleus by fusion if they have enough energy to get in contact with the side of the 249 Bk target.

Quasifission Dynamics in Microscopic Theories

“…In addition, the calculations show that these shell effects strongly depend on the orientation of deformed actinide. Deformed shell effects in the region of 100 Zr have also been invoked to interpret the outcome of TDHF simulations of 40,48 Ca+ 238 U, 249 Bk collisions [37,52].…”

“…A number of theoretical approaches have been developed that describe the quasifission in terms of multi-nucleon transfer (MNT) processes [41,42,43,44,45,46,47]. Recently, time-dependent Hartree-Fock (TDHF) theory have proven to be an excellent tool for studying QF dynamics, and in particular mass-angle distributions and final fragment total kinetic energies (TKE) [48,31,37,49,32,50,51,52,34,53,45,54,55,56]. While the fragments produced in TDHF studies are the excited primary fragments [57] a number of extensions based on the use of Langevin dynamics have been successfully applied to de-excite these fragments [55,58,59,56,60] Theoretical studies of quasifission dynamics have taught us that dynamics themselves may be dominated by shell effects [61,47].…”

Exploring Zeptosecond Quantum Equilibration Dynamics: From Deep-Inelastic to Fusion-Fission Outcomes in Ni58+Ni60Williams1, Sekizawa2, Hinde3 et al. 2018Phys. Rev. Lett.Self Cite495550View full textAdd to dashboardCite

“…, TKE) and impact parameter b, and to examine the origin of the wide mass ratio component, microscopic approaches TDHF and TDRPA have been used. TDHF is a mean-field approach incorporating onebody dissipation that has previously been used to explore dynamical reaction processes such as quasifission [10,[24][25][26][27][28][29][30]. In this work, a 3D TDHF code [31,32], employing the SLy4d parametrization [33] of the Skyrme energydensity functional [34] has been used to explore reaction outcomes for 58,60 Ni+ 60 Ni at the three representative energies shown in Fig.…”

Transport properties of isospin asymmetric nuclear matter using the time-dependent Hartree-Fock method

“…Recent investigations have also shown that the one-body dissipation mechanisms included in TDHF were the most relevant to describe fully damped reactions such as quasi-fission [55][56][57][58][59][60]. In this manuscript we study various aspects of deep-inelastic collisions using the TDHF approach.…”