THE RELATIVISTIC SPIN-ORBIT FORCE NEAR THE NEUTRON DRIP-LINE

The relativistic spin-orbit force and its dependence on neutron excess are studied using the sigma - omega - rho model. By working within th e schematic model of asymmetric semi-infinite nuclear matter we are ab le to isolate the spin-orbit potential and to investigate the followin g aspects: (i) the influence of the spin-orbit force on nuclear surfac e properties as a function of neutron excess, (ii) the local variation of the spin-orbit strength at various asymmetries, and (iii) the depe ndence of the spin-orbit force on the nucleonic isospin. Calculations have been performed for the currently used parameter sets NL1 and NL-S H up to the corresponding neutron-drip line. We conclude that with inc reasing neutron excess the spin-orbit strength drastically decreases w hile its impact on nuclear surface properties depends only slightly on asymmetry. The isospin dependence of the relativistic spin-orbit forc e is negligible.