Nucleon localization and fragment formation in nuclear fission

Abstract

An electron localization measure was originally introduced to characterize chemical bond structures in molecules. Recently, a nucleon localization based on Hartree-Fock densities has been introduced to investigate $\alpha$-cluster structures in light nuclei. Compared to the local nucleonic densities, the nucleon localization function has been shown to be an excellent indicator of shell effects and cluster correlations. Using the spatial nucleon localization measure, we investigate the emergence of fragments in fissioning heavy nuclei. To illustrate basic concepts of nucleon localization, we employ the self-consistent energy density functional method with a quantified energy density functional optimized for fission studies. We study the particle densities and spatial nucleon localization distributions along the fission pathways of ${}^{264}$Fm, ${}^{232}$Th and ${}^{240}$Pu. We demonstrate that the fission fragments are formed fairly early in the evolution, well before scission. We illustrate the usefulness of the localization measure by showing how the hyperdeformed state of ${}^{232}$Th can be understood in terms of a quasimolecular state made of ${}^{132}$Sn and ${}^{100}$Zr fragments. Compared to nucleonic distributions, the nucleon localization function more effectively quantifies nucleonic clustering: its characteristic oscillating pattern, traced back to shell effects, is a clear fingerprint of cluster/fragment configurations. This is of particular interest for studies of fragment formation and fragment identification in fissioning nuclei.

7 pages, 8 figures

References in corpus (8)

• Structure and rotations of the Hoyle state
• Global performance of covariant energy density functionals: ground state observables of even-even nuclei and the estimate of theoretical uncertainties
• Time-dependent electron localization function
• Microscopic description of complex nuclear decay: multimodal fission
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• Localization in light nuclei
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Cited by in corpus (7)

• Formation and distribution of fragments in the spontaneous fission of 240Pu
• Cluster formation in pre-compound nuclei in the time-dependent framework
• Clusterization and deformation of multi-$\Lambda$ hypernuclei within relativistic mean-field model
• Theoretical description of fission yields: towards a fast and efficient global model
• Microscopic description of the torque acting on fission fragments
• Clustering in nuclei at finite temperature
• Two-Center Gaussian potential well for studying light nucleus in cluster structure