Symmetry Energy Of Neutron-rich Nuclear Matter And GDRγ Emission In Intermediate Energy Heavy-ion Collisions

The symmetry energy of nuclear matter, which is important to the research of nuclear physics and astrophysics, is always a hot topic in nuclear physics. The giant dipole resonance(GDR) γ emission phenomenon as a kind of collective movement has become an important probe of studying the dynamical properties, the time scales of the compound nucleus formation and existing, the properties of delayed fission and decay, and so on, which happen in the near-barrier fusion reactions. In this thesis, the intermediate heavy-ion reactions are used to study the symmetry energy of neutron-rich nuclear matter, and the near-barrier fusion reactions are used to study the giant dipole resonance(GDR) γ emission phenomenon.(1)In the framework of modified fisher model and in the grand-canonical ensembles theory, the symmetry energy of neutron-rich nuclear matter is researched in the intermediate heavy-ion reactions. Firstly, the residue Coulomb interaction(RCI), which is a retained term in the study of symmetry energy of neutron-rich fragment in isobaric yield ratio method, is investigated by four approximations. It is found that the M3 and M4 methods are more reasonable and more reliable. Secondly, an isobaric yield ratio difference(IBD) method is proposed to study the difference between the chemical potentials of neutron-proton to temperature(? ?) in intermediate heavy-ion collisions. The ? ? determined by the IBD method is compared to the results of the isoscaling(IS) method. It is found that we can mostly gain the same ? ? by the two methods, and the IBD-? ? is more sensitive to magic nuclei. It can conclude that the IBD method is more reasonable than the IS method. Finally, double ratios(DR) method is used to study the isotopic thermometer( of heavy residues. The result esult shows that most of vary from 0.6 MeV to 2.0 MeV.(2)The GDR γ emission phenomenon is researched in the near-barrier fusion reactions by the EQMD model. We firstly verify the reasonable of EQMD model by comparing the ground state properties obtained from the model with that from the experimental results, including binding energy and root mean square radius of different isotope chains from light to heavy mass region, density distribution, separation energy and the distance between valence nucleon and core of exotic nuclei, and the deformation nuclei is also be studied about its deformation parameter and GDR γ emission. Result shows that the ground state of nuclei is very stable in EQMD, and the model can reproduce the exotic structures of halo nuclei. It can confirm that the EQMD is reasonable. Then we discuss the dependence of GDR γ emission on incident energys, impact parameters and symmetry energy parameters in the near-barrier fusion reactions. It is found that the resonance energy decrease with the increasing incident energy or increasing impact parameters, but increase with the increasing symmetry energy parameters. The range of the resonance energy is from 11.0MeV to 15.0 MeV, which is consistent with the theory anticipation. It can prove that EQMD model can be used to reasonably study heavy-ion fusion at near-barrier energies, which given the possible to research the mechanism of the formation of super-heavy nuclei using fusion reaction.