Fine structure of giant resonances revisited experimentally and theoretically

Abstract

Several examples are presented how the fine structure of collective modes carries unique information on their basic physical properties and, for excitations above the particle thresholds, on the decay mechanisms. The nature of the electric pygmy dipole resonance observed near particle threshold in neutron-rich nuclei is clarified by a detailed study of208Pb Evidence for an orbital magnetic quadrupole twist mode is obtained from a comparison of high-resolution electron and proton scattering experiments on58Ni. An attempt to describe cross sections and spin observables of the 58Ni(p,p′) experiment by state-of-the-art calculations shows surprising deviations. Finally the fine structure of the isoscalar giant quadrupole and the Gamow-Teller resonance in medium-to-heavy nuclei has been studied and new methods to extract the properties of characteristic scales related to the decay properties by wavelet analysis techniques are presented.