Pairing interaction in exotic nuclei: Finite range or zero range?

The proper form of the pairing interaction near the drip line is discussed. The relativistic Hartree-Bogoliubov (RHB) theory in coordinate space is used to describe the chain of even-even nickel isotopes reaching from the proton drip line to the neutron drip line. The pairing correlations are taken into account by both a density-dependent force of zero range and the finite range Gogny force. Through the comparisons of the two neutron separation energies S₂ₙ, the neutron, proton, and matter rms radii, excellent agreement has been found between the calculations with both interactions and the empirical values. The same drip-line nuclei ¹⁰⁰Ni have been predicted. The pairing energies, single particle levels in the canonical bases and their corresponding occupation probabilities have turned out to be similar. It is shown clearly that after proper renormalization (e.g., fixing the corresponding pairing energies here), physical observables such as S₂ₙ and rms radii remain the same, even within a reasonable region of the interaction strength.