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Nuclear Theory·nucl-th

Thursday·November 1, 2018

7 papers—4 primary·3 cross-listed

All7Primary4Cross-lists3
  1. 01

    Isotopic trends of quasifission and fusion-fission in the reactions Ca+Pu

    Lu Guo · Caiwan Shen · Chong Yu · Zhenji Wu

    Background: Quasifission and fusion-fission are primary mechanisms to prevent the production of superheavy elements. The recent experimental measurements reveal that the fusion-evaporation cross section in the reaction channel of Ca+Pu is 50 times lower than using Pu as target nucleus. However, the precise mechanisms of this remarkable isotopic dependence are not well understood. Purpose: To understand the experimental observation of the rapid decrease of stability of superheavy nuclei as the neutron number decreases, the theoretical studies of quasifission and fusion-fission in connection with experimental production for =114 flerovium isotopes are required to investigate the possible differences in reaction mechanisms induced by these two targets. Methods: We propose an approach called TDHF+HIVAP to take into account both the evolution of dinuclear system and the deexcitation of compound nucleus, which combines the microscopic time-dependent Hartree-Fock (TDHF) method for the fusion and quasifission dynamics with the statistical evaporation model HIVAP for fusion-fission dynamics. Results: ......The quantum shell effect displays a crucial role in both the quasifission and the fusion-fission processes. The quasifission is considerably reduced and the survival probability is enhanced around one order of magnitude in the reaction using Pu target as compared to the Pu case. Conclusions: The studies by using TDHF+HIVAP method well account for the experimental observations and the present method clearly shows its applicability in the reaction mechanisms of quasifission and fusion-fission dynamics. The experimental and theoretical results encourage the use of neutron-rich targets for the production of new superheavy elements.

    nucl-thnucl-exPRC(2018)·45 citations
  2. 02

    High squeezed-out n/p ratio as a probe of of the symmetry energy

    Ya-Fei Guo🇨🇳 · Gao-Chan Yong🇨🇳

    By involving the constraints of the slope of nuclear symmetry energy into the question of determination of the high-density symmetry energy, one needs to probe the curvature of nuclear symmetry energy . Based on the Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, effects of the curvature of nuclear symmetry energy on the squeezed-out nucleons are demonstrated in the semi-central Au+Au reaction at 400 and 600 MeV/nucleon. It is shown that the squeezed-out isospin-dependent nucleon emissions at high transverse momenta are sensitive to the curvature of nuclear symmetry energy. The curvature of nuclear symmetry energy at saturation density thus can be determined by the high momentum squeezed-out isospin-dependent nucleon emissions experiments from the semi-central Au+Au reaction at 400 or 600 MeV/nucleon.

    nucl-thnucl-exPRC(2019)·14 citations
  3. 03

    The Statistical Model of Nuclear Reactions: Open Problems

    P. Fanto🇺🇸 · Y. Alhassid🇺🇸 · H. A. Weidenmüller🇩🇪

    Several experiments [1-3] show significant deviations from predictions of the statistical model of nuclear reactions. We summarize unsuccessful recent theoretical efforts to account for such disagreement in terms of a violation of orthogonal invariance caused by the Thomas-Ehrman shift. We report on numerical simulations involving a large number of gamma decay channels that also give rise to violation of orthogonal invariance but likewise do not account for the discrepancies. We discuss the statistical model in the light of these results.

    nucl-thcond-mat.mes-hallCERN Proc.(2019)·0 citations
  4. 04

    Angular momentum of fission fragments

    G.F. Bertsch · T. Kawano · LM. Robledo

    The strong deformation present immediately after scission has consequences for the angular momentum population of the fragments as well as the angular distribution of their decay radiation. We find that the usual spin-cutoff parameterization describes very well the angular momentum distribution associated with the deformation of the fragments at the scission point. Depending on the deformation, its contribution can comparable to the thermal contribution to the angular momentum of the newly formed fragments. The -distribution of the angular momentum is highly polarized and gives rise to large anisotropies in the subsequent gamma cascade. We treat in detail a typical gamma cascade in a daughter nucleus, following usual model assumptions except for the anisotropy of the initial state. In principle, the observed anisotropy can provide information on the relative amounts of deformation and thermal energy present at the scission point.

    nucl-thPRC(2019)·40 citations

Affiliations

first authorsco-authorsvia INSPIRE