Tensor Force Effect on Shape Coexistence of N=28 Neutron-Rich Isotones

The tensor force effect on potential energy surfaces of the N=28 neutron-rich isotones is investigated by using the deformed Skyrme–Hartree–Fock–Bogoliubov approach with the T22 interaction. It is found that, without the tensor force, ⁴⁰Mg and ⁴⁶Ar have prolate and spherical ground states, respectively. The ground states of ⁴²Si and ⁴⁴S are oblate. The shape coexistence in ⁴⁰Mg, ⁴²Si and ⁴⁴S is evident. However, the ground state deformations of these isotones are not changed and the shape coexistence in ⁴²Si and ⁴⁴S vanishes when the tensor force is switched on. Taking ⁴²Si as an example, the disappearance of the shape coexistence is understood by analyzing the tensor force effect on the shell correction energies.