Axially Deformed Relativistic Hartree-fock Theory And The Applications

With the development of nuclear physics for experiments and theories,the research of nuclear physics has been largely extended from a few stable nuclei to several thousands unstable ones,and the investigation of unstable nuclei has become an important basic frontier of nuclear physics.Due to the extreme neutron-proton ratio,the unique weak binding mechanism of unstable nuclei provide a new challenge for studying the nuclear structure,in which the unified treatment of mean field,pair correlation and the related continuum effects are the difficulties in the theories for unstable nuclei.Nuclear force is a basic issue in the nuclear physics.As generally recognized,nuclear force,a residual strong interaction,contains central,strong spin-orbit coupling,and non-central tensor force components.At present,the meson-exchange theory is one of the most successful interpretations of nuclear force.The relativistic mean field(RMF)theory founded on the meson exchange diagram,provides an efficient and predictive tool in exploring the structure properties of nuclei which spread over almost the whole nuclear chart.However,due to the limitation of the Hartree approach,the important de-grees of freedom associated with the?-meson and?-tensor couplings are excluded just for simplic-ity,and the important ingredient of nuclear force——the tensor force components are missing.The relativistic Hartree-Fock(RHF)theory and the extend one,the relativistic Hartree-Fock-Bogoliubov(RHFB)theory,which includes the Fock term explicitly,has revealed the importance of the Fock term in describing the structure of unstable nuclei in the past decade.Besides,as revealed by many experimental and theoretical studies,most of nuclei in nuclear chart,except for a few elements near by the magic numbers,have deformed shapes deviating from spherical symmetry for both ground and exited states.Considering the deformation effects,which can change the microscopic structure of nuclei obviously,is an important prerequisite for reliable description of unstable nuclei.Focusing on the deformed nuclei,the axially deformed relativistic Hartree-Fock(D-RHF)the-ory is developed by utilizing the spherical Dirac Woods-Saxon(DWS)base.The effects of the?-pseudovector and its tensor force components on the structure of deformed nuclei are investi-gated.Taking light nucleus²⁰Ne,medium heavy nucleus⁵⁶Fe and heavy one²²⁰Rn as examples,the truncation convergence check of DWS base is carried out by using the new developed D-RHF code.The rationality and reliability of spherical DWS base are analyzed and demonstrated.The D-RHF theory is applied preliminarily to study the structure properties of²⁰Ne and the shape evo-lution of single particle energy is analyzed.It is shown that the?-pseudovector coupling and its tensor force component have an important influence on the microscopic structure of the deformed nucleus.Meanwhile,the shape evolution of the predicted microstructure is obviously different from that of the traditional theory.Combined with the advantages of RHF theory in dealing with the ten-sor forces,the D-RHF theory provides a reliable theoretical tool for exploring the tensor force effect in deformed nuclei.Considering the advantages of Bogoliubov transformation in describing the mean field and pairing correlation uniformly,the axially deformed relativistic Hartree-Fock-Bogoliubov(D-RHFB)theory,which is the extend of D-RHF theory,is established.Besides,the effect of?-pseudovector and?-tensor couplings on the structure of deformed nucleus is analyzed.Based on the meson ex-change diagram of the Hartree and Fock term,we develop a new scheme for quantizing the nucleon field in Bogoliubov quasiparticle picture,and construct the RHFB system which naturally contains the RHF mean field and the Bogoliubov pair potential.The D-RHFB theory lays a foundation for the systematic development of subsequent theories.Due to the consideration of the Fock term in meson exchange diagram and the covariance of the theory itself,the D-RHFB theory realizes the unified treatment of spin-orbit coupling,tensor force,deformation,pairing correlation and continuum ef-fect,which lays a solid theoretical foundation for the study of unstable nuclei.The completeness of the spherical DWS base is confirmed by the convergence check by using the D-RHFB code for light nucleus²⁴Mg and the mid-heavy one¹⁵⁶Sm,and it indicates that it's necessary of considering the negative energy state in spherical DWS base when calculating heavy nuclei.Combining the qualitative analysis of the coupling properties,it is pointed out that the?-tensor and?-pseudovector couplings introduced by the Fock terms can significantly enhance the deformation effect of the nu-cleus,and improve the quantitative description of the deformed nucleus,such as the ground state of²⁴Mg and¹⁵⁶Sm.Based on the new developed D-RHFB theory,we explore the mechanism behind the novel parity inversion of¹¹Be and halo structure occurrence in^11?14Be,which is uniformly interpreted by the RHF effective interaction PKA1.It is illustrated that the evidently enhanced deformation effects by the?-pseudovector and?-tensor couplings in PKA1 are crucial for correctly describing both even-parity ground state for¹¹Be and neutron halo of^11?14Be.From the spherical shape to largely deformed ground state,the spherical fragment 2s_1/2in^11?14Be remains loosely bound to form the halo,and the intrude fragment 1d_5/2enhances the couplings of the even-parity orbit 1/2₂⁺with the nuclear core to promise the even-parity ground state for¹¹Be,and stabilizes the halo via inherent attractive correlation with the fragment 2s_1/2,which paves a new way to understand the halo pictures in deformed unstable nuclei.