Study Of Heavy-ion Fusion And Breakup Reactions By Quantum Transport Theories

Low-energy heavy-ion collisions are important in nuclear physics. They are thekey way to investigate nuclear structure and nuclear force. When the incident energyis around the Coulomb barrier, the nuclear mean free path is long and the mean fielddominates due to the Pauli principle. In this case nuclear structure and quantum efectsplay important roles, Coulomb repulsive and nuclear attractive interactions also havevery strong interplay. With the increase of the incident energy, nucleon-nucleon colli-sions begin to play a role and there should be a competition between mean field andtwo-body collisions. All these make the reaction mechanism become very complicated.This work is based on quantum many-body theories and the following three points areconcentratedI. Non-central and static deformation efects in low-energy heavy-ion fusion re-actions are investigated by using time-dependent Hatree-Fock (TDHF) and density-constrained TDHF methods. The results indicate that in reactions with spherical pro-jectile and target, both the nucleus-nucleus interaction potential (without centrifugalpotential) and the efective mass parameter depend on the impact parameter. Such de-pendence is enhanced with the increasing system size. When the energy is just abovethe Coulomb barrier, the non-central efect can reduce the fusion cross sections a lot.While at energies high above the Coulomb barrier, the non-central efect has almost noefect on the fusion cross sections. If the projectile or the target is deformed (here onlyprolate deformation is considered), due to the fact that the deformation is associatedwith the change of the single particle levels and shell structures, this is related to quan-tum efects. In this work, such quantum and non-central efects on the fusion excitationfunctions are investigated.II. Energy dissipation in low-energy heavy-ion fusion reactions of mass-symmetricsystems is investigated by adopting the ImQMD model together with the one-dimension macroscopic transport equation. The calculations are repeated by blocking the two-body collisions in ImQMD model to study the relation between one-and two-bodydissipation mechanisms. The results indicate that two-body collisions can reduce theparticle transfer process and thus the one-body dissipation. It’s impossible (at least inthe framework of the one-dimension macroscopic transport equation) one-and two-body dissipation cannot be separated.III. ImQMD model with GEMINI++statistical decay code is used to study theternary breakup mechanism of238U+197Au at15A MeV. In this reaction, binary eventsare rare while the cross sections of ternary and quaternary breakups are comparable(σ3+σ4≈80%σtot) which is essentially diferent from197Au+197Au at15A MeV. TheImQMD model cannot give the right results while the main experimental data can bewell resproduced by using the hybrid model. Analysis of the dynamic process showthat there is a large mass transfer from gold to uranium in the deep-inelastic collision atrelatively small impact parameters.