Evolution of shapes in even–even nuclei using the standard interacting boson model

摘要

The sd-version of the interacting boson model (IBM) is used to establish the shape phase transitional structure. A simplified Hamiltonian is used which is intermediate between the three dynamical symmetries of U(6), namely the spherical U(5), the prolate and oblate deformed SU(3) and the $$gamma $$ γ -unstable O(6) limits. The potential energy surfaces (PESs) to the IBM Hamiltonian have been obtained using the intrinsic state formalism which introduces the shape variables $$eta $$ β and $$gamma $$ γ . The Gadolinium (Gd) and Ruthenium (Ru) isotopic chains have been taken as examples in illustrating the U(5)–SU(3) and U(5)–O(6) shape phase transitions, respectively. We used the standard $$chi ^2$$ χ 2 test to get the IBM Hamiltonian parameters. The fit is performed by minimizing the $$chi ^2$$ χ 2 function for some selected experimental low-lying energy levels, the two neutron separation energies and B(E2) transition rates.