Studies Of Finite Nuclei And Neutronneutron Scattering Cross Section Based On Microscopic Nuclear Force

Nuclear physics is an important basic physical subject,and it is closely connected with astrophysics,the evolution of universe and star.Both theoretical and experimental research of unstable nuclei are one of frontiers of nuclear physics.Starting from the realistic nuclear force,ab-initio approache is one of the focus of theoretical nuclear physics research.Starting from the Bonn nuclear force,we discuss study of nuclear matter within the Dirac-Brueckner-Hartree-Fock approach.Taking into account the short range correlation effect,the saturation properties of symmetry nuclear matter can be explained based on the bare nucleon-nucleon interaction.However,all results of non-relativistic calculation land on the Coester line without the help of three body force.The relativistic DBHF calculations shift the results near to empirical area,providing a density-dependent repulsion effect.The nucleon self-energies are obtained adopting fitting or projection approaches.The choice of covariant operator basis,called subtracted T matrix,is able to correctly treat with the contributions of scalar,vector and pseudo-scalar mesons at the same time,and providing a reliable nucleon self-energies.The density-dependent effective nuclear force of density functional theory is adjusted to the nuclear matter and finite nuclei properties.DFT is widely applied to both nuclei structure and reaction researches.On the other hand,due to the complexities of DBHF,now DBHF is mainly limited to the case of nuclear matter.In recent years,the advance in directly application of DBHF to study finite nuclei have also achieved.Based on nucleon self-energies within DBHF nuclear matter calculation,we finish the parametrization of scalar potential US and vector potential U0 as a function of nucleon density,energy and isospin,and adopt the improved local density approximation(ILDA)to apply directly nucleon self-energies in study of finite nuclei.The density dependence of Us and U0 can be described by a curve,and its coefficients are linearly correlated to nucleon energy,meanwhile the isospin parts are parabola of isospin asymmetry.To describe finite nuclei better,the low-density behavior of nucleon self-energy is constrained by the properties of finite nuclei.According to radial distribution of local nucleon and isospin densities,we obtain the radial distribution of Us and U0.Based on energy dependence of nucleon self-energy,nucleons in various single particle levels are bounded by different US and U0.ILDA means introducing a Gauss distribution to consider the finite volume of nucleon to reproduce the surface effect of finite nuclei.It is concluded that the microscopic calculated nuclear matter effective interaction G matrix can be extended to finite nuclei and obtain fine results.Based on the modern high-precision realistic nuclear force CD-Bonn model,we study the neutron-neutron scattering cross-section,which is one of important input of high density neutron transport calculation.Due to the absence of neutron target,only theoretical calculation can provide predictions.Firstly,within the meson exchange theory for nuclear force,we discuss the contributions of one meson exchange and many meson exchange to charge independence breaking(CIB)and charge symmetry breaking(CSB)of nuclear force.The low energy proton-neutron and proton-proton scattering cross section,and indirect extraction of neutron-neutron scattering length and effective range,are experimental measurements for CIB and CSB.Secondly,based on energy dependence partial wave phase shifts provided by one-boson-exchange CD-Bonn nuclear force,we calculate the neutron-neutron scattering cross-section according to S matrix theory,and compare the results with ENDF/B-?.0 library.It is the first correlative data in China Evaluation Nuclear Data Library.In the case of heavy and superheavy nuclei,? decay is one of main decay channel,up to now there is no great method to calculate alpha decay preformation probability P?.Based on the neutron and proton single particle energy spectra provided by Relativistic Hartree-Bogoliubov model,we define the microscopic valence nucleons(holes)numbers.With the help of NpNn scheme,we propose two simple formulas to calculate P?.P? is related with the nuclear structure of decaying parent nucleus.The valence nucleons located round the Fermi surface can form compact ? particle cluster due to residual interaction.NpNn scheme reflects the linear relationship between valence proton-neutron residual interaction and nucleon collective motions.We calculate P? of Po,Rn,Ra and Th isotopes around the N = 126 shell closure.The calculated P? can reproduce the extracted results from ? decay half-lives.