Deformation evolution and charge radii in even–even W, Os, and Pt isotopes

Abstract

The neutron-deficient even–even isotopes of W, Os, and Pt in the region \(N=98\)–120 provide a valuable framework for investigating shape coexistence and the microscopic drivers of nuclear deformation. Their potential energy curves are calculated using the Skyrme energy density functionals UNEDF1\(^\textrm{SO}\) and SLy4, and the corresponding isotopic evolution of mean-square charge radii is systematically analyzed. The results reveal a general prolate-to-oblate shape transition with increasing neutron number, which occurs around \(N\approx 116\) in the W and Os isotopes and around \(N\approx 110\) in the Pt chain. This transition is accompanied by the emergence of triaxiality at \(N \approx 114\), 112, and 110 for W, Os, and Pt isotopes, respectively. Additionally, the potential energy surfaces become systematically softer along the \(\gamma \) coordinate with increasing proton number Z. We analyze the evolution of the charge radii of the three isotopic chains. The charge radii increase smoothly with increasing neutron number. A pronounced local jump in radii is observed in the Pt isotopes at \(N=110\). This can be attributed to the complicated deformation changes in the \(\beta _2\)-\(\gamma \) plane. In general, the deformation moves toward a smaller \(\beta _2\) with increasing neutron number. In addition, self-consistent blocking calculations for the odd-mass \(^{183,185,193,195,197}\textrm{Pt}\) isotopes demonstrate a strong configuration dependence of nuclear deformation and charge radii, providing microscopic insight into the shape evolution in this mass region.