Structure of Os and Pt isotopes.

Abstract

Employing a pairing-plus-quadrupole model interaction Hamiltonian, especially suited for the Os-Pt region, the ground-state structure of these nuclei for A=186 to 192 is investigated following a self-consistent Hartree-Fock-Bogoliubov approach. Effects of the inclusion of the hexadecapole degrees of freedom in the Hamiltonian are also studied. All the isotopes of osmium considered here come out to be prolate (asymmetry parameter, \ensuremath{\gamma}=0) in shape in the ground state with flat potential-energy surfaces in the \ensuremath{\gamma} direction unless the hexadecapole degrees of freedom are included. $^{186}$,188Pt are triaxial with \ensuremath{\gamma}\ensuremath{\simeq}12\ifmmode^\circ\else\textdegree\fi{}, and $^{190}\mathrm{Pt}$ and $^{192}\mathrm{Pt}$ may be considered as oblate with \ensuremath{\gamma}\ensuremath{\simeq}33\ifmmode^\circ\else\textdegree\fi{} and 44\ifmmode^\circ\else\textdegree\fi{}, respectively. Inclusion of the hexadecapole force does not have much effect on the equilibrium values of shape parameters of Pt isotopes.