TRIPLE-SHAPE COEXISTENCE AND SUPERDEFORMATION IN Pb ISOTOPES

Triple-shape coexistence and superdeformation in Pb isotopes with neutron numbers N = 96-138 is studied. The constrained calculations are performed within the Relativistic Hartree-Bogoliubov (RHB) model using DD-ME2, DD-PC1, and NL3* force parameters, and pairing interaction separable in momentum space. Triple-shape coexistence (spherical, prolate and oblate) manifests themselves in a clear manner in Pb184-190 nuclei with axial RHB calculations. Triaxial RHB calculations further confirm the findings. Superdeformed minimum is observed for Pb188-220 isotopes, and the corresponding excitation energy, deformation and depth of well are comparable within different force parameters used. The behaviour with neutron number of the superdeformed excitation energy, two-neutron separation energy in the ground state and superdeformed minimum, and its differential are fairly reproducing the trend of the available experimental data. The present numerical results are compared with Macro-microscopic Finite Range Droplet Model (FRDM) and Hartree-Fock-Bogoliubov (HFB) model based on the interaction Gogny-D1S force. Overall, a fairly satisfactory agreement is found within the different force parameters and the calculated and experimental results.