Nuclear-structure dependence of the<i>E</i>1 strength located in the giant dipole resonance of heavy nuclei

Abstract

Using monochromatic photons from (n,\ensuremath{\gamma}) and (p,\ensuremath{\gamma}) capture reactions, the elastic scattering of photons was studied in the mass range A=181--238 and energy range E=8--18 MeV. It is shown that the A dependence of the enhancement of E1 strength located in the giant-dipole resonance as revealed by part of the photoneutron cross sections is confirmed by our photon-scattering data. The possibility is discussed that the concentration of E1 strength in the giant dipole resonance may be larger for closed-shell nuclei as compared to open-shell nuclei.