Giant resonance properties in beta stable and unstable nuclei

We study the giant resonances of stable and unstable nuclei in the framewor k of the consistent relativistic random phase approximation built on the no nlinear relativistic mean field (RMF) ground states. The isoscalar and isov ector modes of giant resonances for stable nuclei, such as Pb-208, Sm-144, Sn-116, Zr-90, Ca-40, O-16 and Ca isotope chains are investigated. The cont ribution to the giant resonances from the Dirac sea states and the currents of vector mesons are examined. The results show that the effects of the Di rac sea states on the isoscalar giant modes are pronounced, but become weak er for light nuclei, while the contributions of the isovector modes are neg ligible. The few sets of parameterizations of nonlinear RMF model, which ar e commonly used to give a good description of ground-state properties of fi nite nuclei, could also well describe the nuclear dynamic properties-giant resonances. For nuclei with the extreme value of N/Z, low-lying collective excitations are found in isovector dipole modes, which are mainly due to th e ph excitation of the weakly bound states near Fermi surface and the isosp in mixture effect.