Angular Momentum of Fission Fragments from Microscopic Theory

Abstract

During nuclear fission, a heavy nucleus splits into two rotating fragments. The associated angular momentum is large, yet the mechanism of its generation and its dependence on the mass of fragments remain poorly understood. In this Letter, we provide the first microscopic calculations of angular momentum distributions in fission fragments for a wide range of fragment masses. For the benchmark case of ${}^{239}$Pu($n_{\text{th}}$,f), we find that the angular momentum of the fragments is largely determined by the nuclear shell structure and deformation, and that the heavy fragments therefore typically carry less angular momentum than their light partners. We use the fission model $\mathtt{FREYA}$ to simulate the emission of neutrons and photons from the fragments. The dependence of the angular momenta on fragment mass after the emission of neutrons and statistical photons is linear for the heavy fragments and either constant or weakly linear for the light fragments, consistent with the universal sawtooth pattern suggested by recent experimental data. Finally, we observe that using microscopic angular momentum distributions modifies the number of emitted photons significantly.

7 pages, 2 figures

References in corpus (10)

• Microscopic study of induced fission dynamics of ${}^{226}$Th with covariant energy density functionals
• Generation of fragment angular momentum in fission
• Projection on particle number and angular momentum: Example of triaxial Bogoliubov quasiparticle states
• Fission fragments intrinsic spins and their correlations
• Particle-number projection method in time-dependent Hartree-Fock theory: Properties of reaction products
• Time-dependent generator coordinate method study of mass-asymmetric fission of actinides
• Study of angular momentum effects in fission
• Fission of ${}^{240}$Pu with symmetry-restored density functional theory
• Transfer probabilities for the reactions ${}^{14,20}$O+${}^{20}$O in terms of multiple time-dependent Hartree-Fock-Bogoliubov trajectories
• Improved modeling of photon observables with FREYA

Cited by in corpus (23)

• Theory of Nuclear Fission
• Fission fragments intrinsic spins and their correlations
• Nucleosynthesis and observation of the heaviest elements
• Microscopic analysis of induced nuclear fission dynamics
• Axially-deformed solution of the Skyrme-Hartree-Fock-Bogoliubov equations using the transformed harmonic oscillator basis (IV) hfbtho (v4.0): A new version of the program
• The angular correlation between the fission fragment intrinsic spins
• Spatial orientation of the fission fragment intrinsic spins and their correlations
• Generation, dynamics, and correlations of the fission fragments' angular momenta
• Microscopic description of the torque acting on fission fragments
• Directional-dependence of the event-by-event neutron-$\gamma$ multiplicity correlations in ${}^{252}$Cf(sf)
• Nuclear Quantum Many-Body Dynamics: From Collective Vibrations to Heavy-Ion Collisions (2nd edition)
• Microscopic Calculation of Fission Product Yields for Odd-Mass Nuclei
• Correlations between energy and $\gamma$-ray emission in ${}^{239}\mathrm{Pu}(n,\mathrm{f})$
• New developments in fission studies within the time-dependent density functional theory framework
• Consideration of memory of spin and parity in the fissioning compound nucleus by applying the Hauser-Feshbach fission fragment decay model to photonuclear reactions
• Disentangling the influence of excitation energy and compound nucleus angular momentum on fission fragment angular momentum
• Meaurement of spin vs. TKE of ${}^{144}$Ba produced in spontaneous fission of ${}^{252}$Cf
• Quantum-mechanical description of angular motion of fission fragments at scission
• Microscopic theory of angular momentum distributions across the full range of fission fragments
• Fragment Intrinsic Spins and Fragments' Relative Orbital Angular Momentum in Nuclear Fission
• Angular momentum removal by neutron and $\gamma$-ray emissions during fission fragment decays
• Restoring Broken Symmetries for Nuclei and Reaction Fragments
• Microscopic Theory of Nuclear Fission