Fusion with exotic nuclei using a microscopic approach

Progress in Particle and Nuclear Physics

Barton

2019

The Skyrme effective interaction, with its multitude of parameterisations, along with its implementation using the static and time-dependent density functional (TDHF) formalism have allowed for a range of microscopic calculations of low-energy heavy-ion collisions. These calculations allow variation of the effective interaction along with an interpretation of the results of this variation informed by a comparison to experimental data. Initial progress in implementing TDHF for heavy-ion collisions necessarily used many approximations in the geometry or the interaction. Over the last decade or so, the implementations have overcome all restrictions, and studies have begun to be made where details of the effective interaction are being probed. This review surveys these studies in low energy heavy-ion reactions, finding significant effects on observables from the form of the spin-orbit interaction, the use of the tensor force, and the inclusion of time-odd terms in the density functional.Heavy-ion collisions combine the rich dynamics of a many-body out-of-equilibrium open quantum system with the complexities of the residual part of the strong interaction which leaks out of the small, but neither fundamental or point-like, nucleons, causing them to stick loosely together some of the time, and to fall apart at others. Understanding heavy-ion reactions across all energy scales is necessary to understand stellar nucleosynthesis [1], the synthesis of superheavy nuclei [2,3], the properties of nuclear matter [4][5][6], the QCD phase diagram [7,8] as well as the understanding of reaction mechanisms themselves [9][10][11][12][13].Among the theoretical techniques used to study heavy-ion reactions, methods based on timedependent Hartree-Fock have recently achieved the status of having sufficiently mature implementations free of limiting approximations, and running at a suitable speed, such that systematically varying the effective interaction in the calculations is possible. It is such studies that form the main subject of the present review. The practical implementations, using the Skyrme interaction, are in some sense parameter-free, in that one has a framework using an effective interaction fitted to ground state data and nuclear matter properties, with no further adjustment to dynamics. Structure and reaction effects are together determined self-consistently from the interaction, subject to the approximations of the mean-field and one gives no further adjustment. In another sense, the variation among the sets of available effective interactions are parameters of the calculations. We attempt to summarise here what has been learnt from exploring different Skyrme force parameterisations within low-energy heavy-ion reaction calculations.Overlapping this subject area are other recent review articles, to which the reader is referred: A review in which extensive coverage of theoretical approaches to dynamics of heavy-ion collisions in TDHF and its extensions is presented by Simenel and Umar [14]. This review extensively covers the...

Section: Spin-orbit Interactionsmentioning

confidence: 99%

Section: Spin-orbit Interactionsmentioning

confidence: 99%

Section: Spin-orbit Interactionsmentioning

confidence: 99%

“…Barrier energies A Ca + 116 Sn reactions as a function of mass number of the calcium nucleus. From[101] …”

mentioning

confidence: 99%

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Low-energy heavy-ion reactions and the Skyrme effective interaction

Progress in Particle and Nuclear Physics

Barton

2019

“…For example, one might reasonably expect that when full dynamics is permitted, the ability of the pre-colliding nuclei to change shape will explore a path in which the nuclei can fuse at a lower energy than predicted by FHF. On the other hand, one may find effects in which early transfer of particles actually hinders fusion compared with the simple FHF picture [23]. In any case, the comparison may be physically instructive, and we perform both sets of calucaltions here; FHF and full TDHF calculations to compare barrier heights.…”

Section: Frozen Hartree-fock and Time-dependent Hartree-fockmentioning

confidence: 99%

Role of the Surface Energy in Heavy-Ion Collisions

2020

EPJ Web Conf.

The surface energy is one of the fundamental properties nuclei, appearing in the simplest form of the semi-empirical mass formula. The surface enery has an influence on e.g. the shape of a nucleus and its ability to deform. This in turn could be expected to have an effect in fusion reactions around the Coulomb barrier where dynamical effects such as the formation of a neck is part of the fusion process. Frozen Hartree-Fock and Time-Dependent Hartree-Fock calculations are made for a series of effective interactions in which the surface energy is systematically varied, using 40 Ca + 48 Ca as a test case. The dynamical lowering of the barrier is greatest for the largest surface energy, contrary to naive expectations, and we speculate that this may be due to the variation in other nuclear matter properties for these effective interactions

Mean-field simulations of Es-254 + Ca-48 heavy-ion reactions

2022

Front. Phys.

Einstenium-254 (Z = 99, N = 155), can be prepared as a target for research into nuclear reaction studies. This work presents structure and reaction calculations of Es-254 and Ca-48 (Z = 20, N = 28), using the Skyrme-(Time-Dependent)-Energy-Density-Functional formalism. The reaction calculations show the initial parts of the heavy-ion reaction between the nuclei which, depending on the interaction parameters, can lead to capture to a compound nucleus of element 119. For collisions with the spherical 48Ca impinging on the tip of the prolate 254Es no fusion events are found. For collisions where the calcium approaches the belly of the einsteinium, capture occurs with the compound nucleus outlasting the lifetime of the calculation, indicating a possible fusion candidate. For a sample center-of-mass collision energy of 220 MeV, slightly non-central collisions, up to an impact parameter of 1 fm, also form long-lived compound nuclei.