An interacting boson model Hamiltonian determined from
Hartree-Fock-Bogoliubov calculations with the new microscopic Gogny energy
density functional D1M, is applied to the spectroscopic analysis of
neutron-rich Yb, Hf, W, Os and Pt isotopes with mass A∼180−200.
Excitation energies and transition rates for the relevant low-lying quadrupole
collective states are calculated by this method. Transitions from prolate to
oblate ground-state shapes are analyzed as a function of neutron number N in
a given isotopic chain by calculating excitation energies, B(E2) ratios, and
correlation energies in the ground state. It is shown that such transitions
tend to occur more rapidly for the isotopes with lower proton number Z, when
departing from the proton shell closure Z=82. The triaxial degrees of freedom
turn out to play an important role in describing the considered mass region.
Predicted low-lying spectra for the neutron-rich exotic Hf and Yb isotopes are
presented. The approximations used in the model and the possibilities to refine
its predictive power are addressed.Comment: 12 pages, 7 figures, 1 table, accepted for publication in Phys. Rev.
