On the structure of electric-dipole transitions

Inelastic a scattering at intermediate energies provides a tool for highly selective excitation of isoscalar Giant Resonances. If combined with coincident measurements of decay photons and decay particles the (micro-) structure of the resonances becomes transparent. We have performed neutron decay measurements of the ISGDR in Zr-90, Sn-116 and Pb-208 and photon decay measurements of the Pygmy resonance in Ce-140 at kinematical conditions strongly favouring electric-dipole modes. In result, we got first-time evidence for the direct neutron decay component of the ISGDR in the nuclei under investigation and indications for a surprisingly clear splitting of the Pygmy El strength in Ce-140.