Evidence for the role of proton shell closure in quasi-fission reactions from X-ray fluorescence of mass-identified fragments

Abstract

The atomic numbers and the masses of fragments formed in quasi-fission reactions have been simultaneously measured at scission in 48 Ti + 238 U reactions at a laboratory energy of 286 MeV. The atomic numbers were determined from measured characteristic fluorescence X-rays whereas the masses were obtained from the emission angles and times of flight of the two emerging fragments. For the first time, thanks to this full identification of the quasi-fission fragments on a broad angular range, the important role of the proton shell closure at Z = 82 is evidenced by the associated maximum production yield, a maximum predicted by time dependent Hartree-Fock calculations. This new experimental approach gives now access to precise studies of the time dependence of the N/Z (neutron over proton ratios of the fragments) evolution in quasi-fission reactions.

arXiv comment6 pages, 5 figures, accepted for publication in Phys.Rev.Lett

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• Quasifission dynamics in microscopic theories
• Comparison of fission and quasi-fission modes
• Impact of tensor force on quantum shell effects in quasifission reactions
• Time-dependent Hartree-Fock study of quasifission trajectories in reactions forming ${}^{294}$Og
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• Nuclear Quantum Many-Body Dynamics: From Collective Vibrations to Heavy-Ion Collisions (2nd edition)
• Shell effects in quasi-fission for calcium induced reactions forming thorium isotopes
• The Quest for Superheavy Nuclei: A Theoretical Perspective
• Shell effects in quasifission toward ${}^{180}\mathrm{Hg}$: insights into fission asymmetric modes
• Microscopic quasifission dynamics of the ${}^{54}\text{Cr}+{}^{243}\text{Am}$ reaction