Shape evolution of giant resonances in Nd and Sm isotopes

Giant multipole resonances in Nd and Sm isotopes are studied by employing the quasiparticle-random-phase approximation on the basis of the Skyrme energy-density-functional method. Deformation effects on giant resonances are investigated in these isotopes which manifest a typical nuclear shape change from spherical to prolate shapes. The peak energy, the broadening, and the deformation splitting of the isoscalar giant monopole (ISGMR) and quadrupole (ISGQR) resonances agree well with measurements. The magnitude of the peak splitting and the fraction of the energy-weighted strength in the lower peak of the ISGMR reflect the nuclear deformation. The experimental data on ISGMR, ISGDR, and ISGQR are consistent with the nuclear-matter incompressibility $K \simeq 210-230$ MeV and the effective mass $m^*_0/m \simeq 0.8-0.9$. However, the high-energy octupole resonance (HEOR) in $^{144}$Sm seems to indicates a smaller effective mass, $m^*_0/m \simeq 0.7-0.8$. A further precise measurement of HEOR is desired to determine the effective mass.