Configuration Mixing Calculation In The O(6) Limit Of The Interacting Boson Model

The interacting boson model is extremely successful in describing valence shell and multi-particle-multi-hole excitations in nuclei.Nowadays,the interacting boson model is fundamental in analysis and interpretation of experimental nuclear structural data.When the number of va-lence nucleons or holes is close to a closed shell,especially when the number of protons(5～50and(5～82,multi-particle-hole excitation in the nucleus likely occurs.Due to the fact that the shell model configuration space becomes huge when such multi-particle-hole excitations are taken into account,shell model calculation with multi-particle-hole excitations is not easy to be realized.Nevertheless,the configuration mixing calculation can easily be handled in the interacting boson model.Therefore,it is of practical significance to investigate the configura-tion mixing description with cross shell multi-particle-hole excitations in the interacting boson model.In this thesis,the IBM O（6） soft rotor model suitable to describe-unstable nuclei with two particle-hole excitation is studied in the U（6）[]⊕[+2]model space under the U（6）?O（6）?O（5）?SO（3）?SO（2）basis.A computation code is complied accordingly.As a primary appli-cation,the model is applied to typical-unstable nuclei,^194,196Pt.Level energies,some reduced E2 transition rates,electric quadrupole moments of some low-lying states are systematically fit and compared with the corresponding experimental data.The model calculation shows that the most low-lying level energies,（2）values of the transitions within the valence shell（normal）states of^194,196Pt are fit rather well.It should be emphasized that the model results of the electric quadrupole moments of some low-lying states are much improved in contrast to those of the original O（6）limit theory of the IBM.Furthermore,the low-lying intruder states in^194,196Pt are revealed in this model calculation,which,however,are missing in the original O（6） limit theory of the IBM.