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

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 ɣ-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 β and ɣ. 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 x² test to get the ibm hamiltonian parameters.the fit is performed by minimizing the x² function for some selected experimental low-lying energy levels, the two neutron separation energies and b(e2) transition rates.