Kinetic energy and spin-orbit splitting in nuclei near neutron drip line

Abstract Two important ingredients of nuclear shell-structure, kinetic energy and spin–orbit splitting, are studied as a function of orbital angular momenta l and binding energies, when binding energies of neutrons decrease towards zero. If we use the standard parameters of the Woods–Saxon potential in β stable nuclei and approach the limit of zero binding energy from 10 MeV, the spin–orbit splitting for n=1 orbitals decreases considerably for l=1 , while for l>2 little decreasing is observed in the limit. In contrast, the kinetic energy decreases considerably for l≲3 . The smaller the l values of orbitals, the larger the decreasing rate of both kinetic energy and spin–orbit splitting. The dependence of the above observation on the diffuseness of potentials is studied.