Microscopic linear response calculations based on the Skyrme functional plus the pairing contribution

A self-consistent quasiparticle random-phase approximation (QRPA) model that employs the canonical Hartree-Fock-Bogoliubov (HFB) basis and an energy-density functional with a Skyrme mean-field part and a density-dependent pairing is used to study the monopole collective excitations of spherical even-even nuclei. The influence of the spurious state on the strength function of the isoscalar monopole excitations is clearly assessed. We compare the effect of different kinds of pairing forces (volume pairing, surface pairing, and mixed pairing) on the monopole excitation strength function. The energy of the isoscalar giant monopole resonance (ISGMR), which is related to the nuclear incompressibility K-infinity, is calculated for tin isotopes and the results are discussed.