Further Study Of Quantum Phase Transition Of Nuclei

Interacting Boson Model(IBM) is a algebraic model which is usually used to study the nuclear collective behavior and thus the possible new symmetry could be obtained.Based on IBM, we introduce two different kinds of higher-order terms to study the quantum phase transition of transitional nuclei.One work is to study the structure of transitional nuclei with X(5) symmetry from the spherical to the axially deformed limit. The new O(6) higher-order term [Q(0)×Q(0)×Q(0)](0) is introduced to study the structure of150Nd nucleus with X(5) symmetry within the IBM. Two schemes are used, one is U(5)-SU(3) scheme using SU(3) quadrupole-quadrupole interaction, and another is UQ scheme in which the O(6) higher-order terms is used to replace the previous one. We calculate the energy levels, the intraband and interband transition B(E2) values. The results show that both schemes can describe the150Nd nucleus with X(5) symmetry. Also the overall fitting quality of the UQ scheme is better than that of the U(5)-SU(3) scheme, especially in higher excited states and γ band and the interband B(E2) transitions in150Nd nucleus.Another work is to introduce the different [Q(ξ)×Q(ξ×Q(ξ)](0) higher-order term to study the possible triaxial deformation of nuclei. The energy of ground state is investigated when changing the number of bosons and different control parameters. The results show that this higher-order term could explain triaxial deformation of ground state. The application is also made for nuclei of192Pt and188Os and the results show that the effect of higher-order term seems obvious.