Direct Observation of Elastic and Inelastic Photon Scattering by the Giant Dipole Resonance inNi60

Abstract
Monoenergetic photons and a high-resolution NaI spectrometer have been used to measure the absolute 120° scattering cross sections to the ground state and to the first excited state in Ni60 for excitations between 15 and 22 MeV. The inelastic scattering to the first excited state was found to be about 15% of the elastic throughout this energy range. Our results do not appear to be in quantitative agreement with the predictions of the dynamic collective model.