Effect of the neutron skin on collective states of nuclei

Abstract
The effect of a neutron skin on the collective states of medium and heavy-mass nuclei is discussed. We consider two well-known collective modes which correspond to the motion of neutrons with respect to protons, namely, the M1 (scissors) and the isovector E1 (giant dipole) resonance. For nuclei with a sufficient excess of neutrons the behavior of the ‘‘pygmy resonance’’ is also discussed.