Excitations of pygmy dipole resonances in exotic and stable nuclei via Coulomb and nuclear fields

Abstract

We study heavy-ion inelastic scattering processes in neutron-rich nuclei including the full response to the different multipolarities. Among these we focus in particular on the excitation of low-lying dipole states commonly associated to the pygmy dipole resonance. The multipole response is described within the Hartree-Fock plus RPA formalism with Skyrme interaction. We show how the combined information from reactions processes involving the Coulomb and different mixtures of isoscalar and isovector nuclear interactions can provide a clue to reveal the characteristic features of these states. We have performed calculation for the excitation of ${}^{132}$Sn generated in the reactions with ${}^{4}$He, ${}^{40}$Ca, and ${}^{48}$Ca at several incident energies, as well as for the system ${}^{17}$O $+{\phantom{\rule{0.28em}{0ex}}}^{208}$Pb. Our results suggest that the investigation of the PDR states can be better carried out at low incident energies (below 50 MeV/nucleon). In fact, at these energies the PDR peak is relatively stronger than the giant dipole resonance (GDR) one and the narrow width of the low-lying quadrupole and octupole states should not blur its presence.