Z(5): Critical Point Symmetry for the Prolate to Oblate Nuclear Shape Phase Transition

A critical point symmetry for the prolate to oblate shape phase transition is intro­ duced, starting from the Bohr Hamiltonian and approximately separating variables for γ=30°. Parameter-free (up to overall scale factors) predictions for spectra and B(E2) transition rates are found to be in good agreement with experimental data for 194Pt, which is supposed to be located very close to the prolate to oblate critical point, as well as for its neighbours (192Pt, 196Pt).

ROTATIONAL DRIVEN NUCLEAR SHAPE PHASE TRANSITION OF THE YRAST STATES OF INDIVIDUAL NUCLEUS IN INTERACTING BOSON MODEL

With the intrinsic coherent state formalism and the angular momentum projection, we study the shape phase structure of the yrast states in the dynamical symmetries of the IBM. We found that the states in the U (5) symmetry can undergo a rotation driven vibrational to axially rotational shape phase transition if the interaction parameters take negative values smaller than the critical ones. It shows that the U (5) symmetry of the IBM1 is an appropriate approach to describe the rotation driven shape phase transition along the yrast line of individual nucleus as the interaction parameters are taken in a special region. The O (6) symmetric yrast states may involve a phase transition from γ-soft rotation to triaxial rotation as the angular momentum increases, if the interaction parameters are specially chosen. And the yrast states in SU (3) symmetry always appear in the axially prolate shape phase.