IBM And Higher Order Terms And Their Applications In Ba Isotopes

Nuclear structure and its shape quantum phase transition has been the frontier research field of nuclear physics.The interacting boson model(IBM)is an algebraic model which is suitable to study the collective motion of nuclei.And it can be used to analyze the structure and properties of nuclei in the transition region.In this paper,the high-order term interaction is introduced into the IBM model.We study the quantum phase transition behavior in the extended Casten triangular transition region,and further apply this model to study the properties of Ba isotopes of Z=56.Firstly,the quantum phase transition behavior in the extended Casten triangular transition region is studied by introducing the higher-order terms.We make a qualitative analysis of some physical quantities,including the energy levels and the quadrupole transition reduced probability and their ratios,discussing their changes with the control parameters.We also analyze their changes with the boson number,with and without U(5)changes.The results show that high-order terms have large effects on the system.Then,we apply to investigate the Ba isotope nuclei with Z=56.By considering U(5)term,the energy levels and the quadrupole transition probabilities of Ba isotope chain are calculated with and without higher-order terms,respectively,and compared with the experimental data.The results show that the experimental data can be better described by the theoretical values with higher-order terms.We further study the BE(2)interband transitions of Ba isotopes without considering the U(5)term.It is found that the experiment data can be explained reasonably only by the IBM with higher-order terms.It is impossible to explain the data in the SU(3)limit model of the literature,since the interband transition is almost forbidden.It is shown that the IBM with higher-order term is superior to the SU(3)limit model.