Abstract :
High resolution photon scattering experiments with very high sensitivity have been performed at the superconducting Darmstadt electron accelerator S-DALINAC. The energy range from about 3 MeV up to the nucleon separation energy has been investigated. The electric dipole strength distributions measured in this way show a concentration of strength in the 1ħ region exhausting up to one percent of the isovector Energy Weighted Sum Rule (EWSR) for various nuclei. A systematic study on the N=82 isotonic chain seems to hint to a correlation of the summed strength with the nucleon skin.
