Excitation Modes of Nuclei Far from Stability*

Abstract

Excitation modes of nuclei far from stability are studied performing the Hartree-Fock plus RPA calculation with the Skyrme interaction. It is found that there are giant excitation peaks, referred to as giant neutron modes, below the isoscalar giant resonances in nuclei with the neutron skin, and that these peaks consist practically of neutron excitations only. Their transition densities are shown to be extended radially in comparison to those of the isoscalar giant resonances. A strong correlation between the sum of the transition strength of the giant neutron modes and the number of neutrons in the neutron skin is found. It is also found that the neutron modes can be seen in excitations with various multipolarities. However, the magnitude of each neutron mode varies according to its multipolarity. Proton mode excitations can be formed in proton-rich nuclei similarly to nuclei with the neutron skin, but their strengths are not so prominent as those of the neutron modes.