We multiply them with cutoff factors depending on the single-particle energy. For the form of the cutoff function, see Refs. [TTO96a] This cutoff function is very important because in the BCS treatment of nuclei far from the beta-stability line, one has to take care so that the continuum states are not occupied, which give rise to unphysical nucleon gas extending over the entire box.
In order to treat a wide range of nuclei on a single footing, we need a prescription to determine the strength for each nucleus. For this purpose, we have developed a method based on the continuous spectrum approximation which uses the semiclassical single-particle level density obtained in the Thomas-Fermi approximation. We replace the strength with 0.6 MeV when it exceeds 0.6 MeV.
It should be kept in mind that a more accurate treatment of the pairing is necessary for deformed and/or near-drip-line nuclei than for spherical stable nuclei. One should not underestimate the importance of the pairing from one's experience with stable and spherical nuclei. The pairing correlation influences on the deformation as well as on the location of the neutron drip line. For example, one can see in Ref. [TBF93] that the potential energy curve of 186Pb is substantially changed when the pairing interaction strength is slightly reduced. Similar example of 80Zr is discussed in this paper.