Shape evolution of thorium isotopes in between the drip-lines

Abstract

Commonly encountered shapes in nuclei are spherical, prolate and oblate. The shape of a nucleus is decided by the residual interactions among its nucleons. In our current investigation, we incorporate both axial and triaxial degrees of freedom to study how the shape of thorium nuclei changes within the boundaries of the drip lines. We employed the relativistic mean-field theory and utilized density-dependent meson-exchange as the functional throughout our calculations. We calculated the total binding energy as it varies with the deformation parameter [Formula: see text] and subsequently depicted the resulting binding energy curves. Furthermore, we examined the self-consistent energy surface for thorium isotopes with triaxial quadrupole deformations. The emergence of potential energy minima can be attributed to the presence of gaps or regions with reduced density of single-particle energy levels around the Fermi surface, as the nucleus undergoes deformation. The nuclear shape evolution of thorium isotopes ranging from [Formula: see text] to [Formula: see text] was investigated, [Formula: see text] and [Formula: see text] are spherical in shape and the nearby isotopes are less deformed and nearly spherical. Isotopes ranging from [Formula: see text] to [Formula: see text] exhibit a higher level of deformation. The most deformed nucleus is [Formula: see text] and is prolate. The weak triaxial behavior is observed within the region associated with shape phase transition.