Collective aspects deduced from time-dependent microscopic mean-field with pairing: Application to the fission process

Tanimura, Yusuke; Lacroix, Denis; Scamps, Guillaume

doi:10.1103/physrevc.92.034601

Cited by 52 publications

(72 citation statements)

References 27 publications

(55 reference statements)

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“…As noted in [27], it can describe the average kinetic energy of fragments after fission. The inclusion of pairing effects significantly extend the applicability of this approach [15,28]. As shown in Ref.…”

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confidence: 99%

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Microscopic Phase-Space Exploration Modeling ofFm258Spontaneous Fission

2017

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We show that the total kinetic energy (TKE) of nuclei after the spontaneous fission of 258 Fm can be well reproduced using simple assumptions on the quantum collective phase-space explored by the nucleus after passing the fission barrier. Assuming energy conservation and phase-space exploration according to the stochastic mean-field approach, a set of initial densities is generated. Each density is then evolved in time using the nuclear time-dependent density-functional theory with pairing. This approach goes beyond mean-field by allowing spontaneous symmetry breaking as well as a wider dynamical phase-space exploration leading to larger fluctuations in collective space. The total kinetic energy and mass distributions are calculated. New information on the fission process: fluctuations in scission time, strong correlation between TKE and collective deformation as well as pre-scission particle emission, are obtained. We conclude that fluctuations of TKE and mass are triggered by quantum fluctuations.PACS numbers: 21.60. Jz, 24.75.+i, 25.85.Ca, 27.90.+b The dynamical modeling of a nuclear Fermi quantum droplet that spontaneously breaks into two pieces represents one of the most exciting challenges of nuclear physics today. Beside its description, a deeper microscopic understanding of spontaneous fission (SF) is of great importance to form the heaviest elements at the frontier of the nuclear chart [1][2][3] or to further improve our knowledge about the competition between the r-process and fission during the primordial nucleosynthesis [4]. Motivated also by its importance in nuclear energy production, intensive experimental efforts have been made to accumulate precise measurements [5][6][7][8][9]. In recent years, an increasing effort was made to remove empirical ingredients that are employed in macroscopic modeling of fission and use microscopic theories [10,11]. The nuclear Density Functional Theory (DFT) is a suitable starting point to describe some aspects related to the large amplitude collective motion (LACM). A minimal information obtained from DFT is the adiabatic collective energy landscape [11]. One challenge to describe spontaneous fission (SF) is the necessity to explicitly treat the evolution as a quantum dynamic in collective space. Progresses have been made with the Time-Dependent Generator Coordinate Method (TDGCM) [12][13][14]. This theory by treating quantally collective degrees of freedom (DOF) is promising. However, the adiabatic assumption often made becomes critical especially close to scission [15]. Dissipation of the collective motion into internal excitations also plays a key role to understand the excitation energy and kinetic energy sharing during fragments separation [16]. Understanding this dissipation requires to include many-body states beyond the adiabatic limit [17]. It is yet unclear how the pre-scission neutron and proton emissions can be incorporated in the TDGCM.The nuclear time-dependent DFT (TDDFT) overcomes some of these limitations. With recently developed symmetry unrest...

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“…This theory by treating quantally collective degrees of freedom (DOF) is promising. However, the adiabatic assumption often made becomes critical especially close to scission [15]. Dissipation of the collective motion into internal excitations also plays a key role to understand the excitation energy and kinetic energy sharing during fragments separation [16].…”

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Microscopic Phase-Space Exploration Modeling ofFm258Spontaneous Fission

2017

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“…As shown in Ref. [21], the diagonalization of the mass gives new canonical pairs of operators (Q k ,P k ), whose commutation rules identify with the TDRPA ones and are given by…”

Section: Generalization To Several Collective Degrees Of Freedommentioning

confidence: 99%

“…The fact that Q th 2 is well beyond the expected barrier position signs the deviation from the adiabatic limit of the microscopic transport theory close to single-particle level crossings (See Refs. [13][14][15][16]21]). …”

Section: Application To the Fission Of 258 Fmmentioning

confidence: 99%

Collective aspects of microscopic mean-field evolution along the fission path

Tanimura

Lacroix

Scamps

2016

EPJ Web of Conferences

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Abstract. We propose a new method to extract the collective masses and momenta associated with a given set of collective coordinates, along a dynamical microscopic mean-field evolution. We apply our method to the symmetric fission of 258 Fm nucleus, and analyze the dynamical evolution of the system in the collective space. We compare, between the dynamical and the adiabatic paths, the force acting on the quadrupole degree of freedom, which is closely related to the relative distance between fragments. It is shown that dynamical effects beyond the adiabatic limit are important for formation and scission of the neck between emitted fragments.

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“…Nevertheless as shown in ref. [17,18], within mean-field dynamics theories, the fission process does not occur for too compact shape.…”

Section: Two-body Observablesmentioning

confidence: 99%

Microscopic description of²⁵⁸Fm fission dynamic with pairing

Scamps

Simenel

Lacroix

2016

EPJ Web of Conferences

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Fission dynamic remains a challenge for nuclear microscopic theories. In order to understand the dynamic of the last stage of the fission process, the time-dependent Hartree-Fock approach with BCS pairing is applied to the describe the fission of the 258 Fm. A good agreement is found for the one-body observables: the total kinetic energy and the average mass asymmetry. The non-physical dependence of two-body observables with the initial shape is discussed.

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Collective aspects deduced from time-dependent microscopic mean-field with pairing: Application to the fission process

Cited by 52 publications

References 27 publications

Microscopic Phase-Space Exploration Modeling ofFm258Spontaneous Fission

Microscopic Phase-Space Exploration Modeling ofFm258Spontaneous Fission

Collective aspects of microscopic mean-field evolution along the fission path

Microscopic description of²⁵⁸Fm fission dynamic with pairing

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Collective aspects deduced from time-dependent microscopic mean-field with pairing: Application to the fission process

Cited by 52 publications

References 27 publications

Microscopic Phase-Space Exploration Modeling ofFm258Spontaneous Fission

Microscopic Phase-Space Exploration Modeling ofFm258Spontaneous Fission

Collective aspects of microscopic mean-field evolution along the fission path

Microscopic description of258Fm fission dynamic with pairing

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Microscopic description of²⁵⁸Fm fission dynamic with pairing