Structure of low-energy excitations in skin nuclei

We present theoretical investigations based on self-consistent HFB and QPM calculations on dipole and other multipole excitations in N=50, 82 and Z=50 nuclei, particularly exploring their connection to the thickness of the neutron or proton skin, respectively. From the analysis of the structure of low-energy electric dipole and quadrupole states and the corresponding neutron and proton transition densities, PDR and PQR modes are identified as distinct and unique excitations, different from giant resonances and collective low-energy excitations in the quadrupole case, respectively. The total PDR and PQR strengths are found to be related to the neutron or proton skin thicknesses. Furthermore, recent calculations of low-energy E1 and spin-flip M1 excitations in N=82 nuclei are presented in comparison with experimental data. These investigations allow to decompose the dipole strength below the GDR to elastic E1 component, related to skin oscillations and background component composed of elastic and inelastic E1 and M1 transitions, respectively. The obtained information reveals new aspects in the isospin dynamics of the nucleus.