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Stetcu I, Lovell AE, Talou P, Kawano T, Marin S, Pozzi SA, Bulgac A. Angular Momentum Removal by Neutron and γ-Ray Emissions during Fission Fragment Decays. Phys Rev Lett 2021; 127:222502. [PMID: 34889623 DOI: 10.1103/physrevlett.127.222502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 10/15/2021] [Accepted: 10/26/2021] [Indexed: 06/13/2023]
Abstract
We investigate the angular momentum removal from fission fragments (FFs) through neutron and γ-ray emission, finding that about half the neutrons are emitted with angular momenta ≥1.5ℏ and that the change in angular momentum after the emission of neutrons and statistical γ rays is significant, contradicting usual assumptions. Per fission event, in our simulations, the neutron and statistical γ-ray emissions change the spin of the fragment by 3.5-5ℏ, with a large standard deviation comparable to the average value. Such wide angular momentum removal distributions can hide any underlying correlations in the fission fragment initial spin values. Within our model, we reproduce data on spin measurements from discrete transitions after neutron emissions, especially in the case of light FFs. The agreement further improves for the heavy fragments if one removes from the analysis the events that would produce isomeric states. Finally, we show that while in our model the initial FF spins do not follow a sawtoothlike behavior observed in recent measurements, the average FF spin computed after neutron and statistical γ emissions exhibits a shape that resembles a sawtooth. This suggests that the average FF spin measured after statistical emissions is not necessarily connected with the scission mechanism as previously implied.
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Affiliation(s)
- I Stetcu
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - A E Lovell
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - P Talou
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - T Kawano
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - S Marin
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - S A Pozzi
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - A Bulgac
- Department of Physics, University of Washington, Seattle, Washington, D.C. 98195-1560, USA
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Stetcu I, Bertulani CA, Bulgac A, Magierski P, Roche KJ. Relativistic Coulomb excitation within the time dependent superfluid local density approximation. Phys Rev Lett 2015; 114:012701. [PMID: 25615463 DOI: 10.1103/physrevlett.114.012701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Indexed: 06/04/2023]
Abstract
Within the framework of the unrestricted time-dependent density functional theory, we present for the first time an analysis of the relativistic Coulomb excitation of the heavy deformed open shell nucleus (238)U. The approach is based on the superfluid local density approximation formulated on a spatial lattice that can take into account coupling to the continuum, enabling self-consistent studies of superfluid dynamics of any nuclear shape. We compute the energy deposited in the target nucleus as a function of the impact parameter, finding it to be significantly larger than the estimate using the Goldhaber-Teller model. The isovector giant dipole resonance, the dipole pygmy resonance, and giant quadrupole modes are excited during the process. The one-body dissipation of collective dipole modes is shown to lead a damping width Γ(↓)≈0.4 MeV and the number of preequilibrium neutrons emitted has been quantified.
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Affiliation(s)
- I Stetcu
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - C A Bertulani
- Department of Physics and Astronomy, Texas A & M University-Commerce, Commerce, Texas 75429, USA
| | - A Bulgac
- Department of Physics, University of Washington, Seattle, Washington 98195-1560, USA
| | - P Magierski
- Department of Physics, University of Washington, Seattle, Washington 98195-1560, USA and Faculty of Physics, Warsaw University of Technology, ulica Koszykowa 75, 00-662 Warsaw, Poland
| | - K J Roche
- Department of Physics, University of Washington, Seattle, Washington 98195-1560, USA and Pacific Northwest National Laboratory, Richland, Washington 99352, USA
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Wlazłowski G, Holt JW, Moroz S, Bulgac A, Roche KJ. Auxiliary-field quantum Monte Carlo simulations of neutron matter in chiral effective field theory. Phys Rev Lett 2014; 113:182503. [PMID: 25396365 DOI: 10.1103/physrevlett.113.182503] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Indexed: 06/04/2023]
Abstract
We present variational Monte Carlo calculations of the neutron matter equation of state using chiral nuclear forces. The ground-state wave function of neutron matter, containing nonperturbative many-body correlations, is obtained from auxiliary-field quantum Monte Carlo simulations of up to about 340 neutrons interacting on a 10(3) discretized lattice. The evolution Hamiltonian is chosen to be attractive and spin independent in order to avoid the fermion sign problem and is constructed to best reproduce broad features of the chiral nuclear force. This is facilitated by choosing a lattice spacing of 1.5 fm, corresponding to a momentum-space cutoff of Λ=414 MeV/c, a resolution scale at which strongly repulsive features of nuclear two-body forces are suppressed. Differences between the evolution potential and the full chiral nuclear interaction (Entem and Machleidt Λ=414 MeV [L. Coraggio et al., Phys. Rev. C 87, 014322 (2013).
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Affiliation(s)
- G Wlazłowski
- Faculty of Physics, Warsaw University of Technology, Ulica Koszykowa 75, 00-662 Warsaw, Poland and Department of Physics, University of Washington, Seattle, Washington 98195, USA
| | - J W Holt
- Department of Physics, University of Washington, Seattle, Washington 98195, USA
| | - S Moroz
- Department of Physics, University of Washington, Seattle, Washington 98195, USA
| | - A Bulgac
- Department of Physics, University of Washington, Seattle, Washington 98195, USA
| | - K J Roche
- Department of Physics, University of Washington, Seattle, Washington 98195, USA and Pacific Northwest National Laboratory, Richland, Washington 99352, USA
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Abstract
Using ensembles of two, three, and four spheres immersed in a fermionic background we evaluate the (integrated) density of states and the Casimir energy. We thus infer that for sufficiently smooth objects, whose various geometric characteristic lengths are larger then the Fermi wave length one can use the simplest semiclassical approximation (the contribution due shortest periodic orbits only) to evaluate the Casimir energy. We also show that the Casimir energy for several objects can be represented fairly accurately as a sum of pairwise Casimir interactions between pairs of objects.
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Affiliation(s)
- A Bulgac
- Department of Physics, University of Washington, Seattle, WA 98195-1560, USA
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Abstract
The positioning of a bubble inside a many fermion system does not affect the volume, surface, or curvature terms in the liquid drop expansion of the total energy. Besides possible Coulomb effects, the only other contribution to the ground state energy of such a system arises from shell effects. We show that the potential energy surface is a rather shallow function of the displacement of the bubble from the center and in most cases the preferential position of a bubble is off-center. Systems with bubbles are expected to have bands of extremely low lying collective states, corresponding to various bubble displacements.
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Affiliation(s)
- Y Yu
- Department of Physics, University of Washington, Seattle, Washington 98195-1560, USA
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Bulgac A, Kusnezov D. Random matrix approach to quantum dissipation. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1996; 54:3468-3478. [PMID: 9965491 DOI: 10.1103/physreve.54.3468] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Bulgac A, Lewenkopf C, Mickrjukov V. Generalized local approximation to the exchange potential. Phys Rev B Condens Matter 1995; 52:16476-16485. [PMID: 9981046 DOI: 10.1103/physrevb.52.16476] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Bulgac A, Frankfurt L. Coherent effects, parton distributions, and baryon rich matter in central high energy heavy ion collisions. Phys Rev D Part Fields 1993; 48:R1894-R1898. [PMID: 10016480 DOI: 10.1103/physrevd.48.r1894] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Bulgac A. Time-dependent Hartree-Fock-Bogoliubov approximation and nonintegrable quantum phase. Phys Rev C Nucl Phys 1990; 41:2333-2339. [PMID: 9966598 DOI: 10.1103/physrevc.41.2333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Walet NR, Klein A, Bulgac A. Generalized valley approximation applied to a schematic model of the monopole excitation. Phys Rev C Nucl Phys 1990; 41:318-328. [PMID: 9966345 DOI: 10.1103/physrevc.41.318] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Bulgac A. Symplectic structure of the collective manifold. Phys Rev C Nucl Phys 1989; 40:2840-2843. [PMID: 9966293 DOI: 10.1103/physrevc.40.2840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Bulgac A. Configurational quasidegeneracy and the liquid drop model. Phys Rev C Nucl Phys 1989; 40:1073-1076. [PMID: 9966073 DOI: 10.1103/physrevc.40.1073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Bulgac A, Klein A, Walet NR. Adiabatic time-dependent Hartree-Fock theory in the generalized valley approximation. Phys Rev C Nucl Phys 1989; 40:945-959. [PMID: 9966059 DOI: 10.1103/physrevc.40.945] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Bulgac A. Effective action for a nonadiabatic quantum process. Phys Rev A Gen Phys 1988; 37:4084-4089. [PMID: 9899530 DOI: 10.1103/physreva.37.4084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Bulgac A, Klein A. Decoupling a collective degree of freedom from a model for tunneling in many-particle systems. Phys Rev C Nucl Phys 1988; 37:2156-2161. [PMID: 9954683 DOI: 10.1103/physrevc.37.2156] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Bulgac A, Klein A. Determination of the collective Hamiltonian in a self-consistent theory of large amplitude adiabatic motion. Phys Rev C Nucl Phys 1987; 36:2661-2671. [PMID: 9954392 DOI: 10.1103/physrevc.36.2661] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Bulgac A, Klein A. Application of a theory of large amplitude collective motion to a generalized landscape model. Phys Rev C Nucl Phys 1987; 36:2672-2679. [PMID: 9954393 DOI: 10.1103/physrevc.36.2672] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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