Nuclear compression modulus, isotope shifts and effective mass

Isotope shifts of Pb nuclei are studied by taking into account giant monopole and quadrupole resonances by a perturbative method. Giant monopole states are calculated by the Hartree-Fock and random phase approximation response function method using three parameter sets of the Skyrme interaction SGI, SGII and SIII which give the compression moduli K∞ = 269 MeV, 217 MeV and 356 MeV, respectively. Our calculations reproduce the kink of the observed isotope shifts at 208Pb, while the second-order effect due to the giant quadrupole resonances is not enough to explain the observed odd-even staggering. The Skyrme force SGII having K∞ = 218 MeV shows the best quantitative agreement among three forces with the experimental systematics of the isotope shifts of Pb nuclei. The effects of the effective mass is also discussed. (author)