Shell Effects in Quasi-fission in Reactions Forming 226Th Compound Nucleus

Abstract

Quasi-fission (QF) reactions occur in fully damped heavy-ion collisions without the formation of an equilibrated compound nucleus, leading to the formation of fragments with similar properties as in fission reactions. Similar shell effects are expected to affect fragment formation in both fission and QF. Our purpose is to investigate QF dynamics in different reactions forming the same compound nucleus and search for possible signatures of shell effects in fragment formation. 50Ca+176Yb and 96Zr+130Sn QF reactions are simulated with the time-dependent Hartree-Fock code Sky3D near the Coulomb barrier. Evolutions of the quadrupole (Q20) and octupole (Q30) moments are interpreted in terms of features of the potential energy surface (PES) of the 226Th compound nucleus. Both reactions encounter QF. In 50Ca+176Yb, those only occur at finite angular momenta. In the more symmetric 96Zr+130Sn reaction with stronger Coulomb repulsion in the entrance channel, QF also occurs in central collisions. In agreement with earlier predictions, 50Ca+176Yb encounters partial mass equilibration that is stopped when the heavy fragment reaches Z~54 protons, as in the asymmetric fission mode of 226Th. 96Zr+130Sn encounters an inverse QF also leading to similar fragments as in asymmetric fission. In both systems, QF trajectories in the Q20-Q30 plane follow the asymmetric fission valley of 226Th PES. The observation of an inverse QF is a clear prediction that shell effects have a strong influence in QF. The similarity between fragments formed in asymmetric fission and QF supports the idea that the same shell effects are at play in both mechanisms. Interpreting QF dynamics with PES used in fission is naturally limited by the fact that these PES are usually computed with axial symmetry, no angular momentum and no excitation energy, thus motivating future developments of PES for QF.

References in corpus (17)

• Interplay between quantum shells and orientation in quasi-fission
• TDHF Theory and Its Extensions for the Multinucleon Transfer Reaction: a Mini Review
• Nuclear-fission studies with relativistic secondary beams: analysis of fission channels
• Dissipative dynamics in quasi-fission
• New neutron-rich isotope production in ${}^{154}$Sm+${}^{160}$Gd
• A new inverse quasifission mechanism to produce neutron-rich transfermium nuclei
• Timescales of quantum equilibration, dissipation and fluctuation in nuclear collisions
• Reduced quasifission competition in fusion reactions forming neutron-rich heavy elements
• Exploring Zeptosecond Quantum Equilibration Dynamics: From Deep-Inelastic to Fusion-Fission Outcomes in ${}^{58}$Ni+${}^{60}$Ni Reactions
• Transport properties of isospin asymmetric nuclear matter using TDHF
• Evidence for the role of proton shell closure in quasi-fission reactions from X-ray fluorescence of mass-identified fragments
• Comparison of fission and quasi-fission modes
• Time-dependent Hartree-Fock study of quasifission trajectories in reactions forming ${}^{294}$Og
• Impact of tensor force on quantum shell effects in quasifission reactions
• Hartree-Fock-Bogoliubov study of quantum shell effects on the path to fission in ${}^{180}$Hg, ${}^{236}$U and ${}^{256}$Fm
• Experimental evidence of the effect of nuclear shells on fission dissipation and time
• Simulation of fusion and quasi-fission in nuclear reactions leading to production of superheavy elements using the Constrained Molecular Dynamics model

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• Nuclear Quantum Many-Body Dynamics: From Collective Vibrations to Heavy-Ion Collisions (2nd edition)
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• Microscopic quasifission dynamics of the ${}^{54}\text{Cr}+{}^{243}\text{Am}$ reaction
• Shell effects in quasifission toward ${}^{180}\mathrm{Hg}$: insights into fission asymmetric modes
• The Quest for Superheavy Nuclei: A Theoretical Perspective