The structure of low-lying excited states of spherical nuclei

Abstract

The change of the structure of low-lying excited states of even–even spherical nuclei in going from closed-shell to transitional nuclei is studied using the quasiparticle–phonon model. The transition charge densities of these states and the distribution of electromagnetic transition strengths are investigated for excitation energies of up to 5 MeV. The properties of low-lying 1 − states and states forming pygmy resonances are analyzed. The anomalous behavior of the photoexcitation cross sections of isomers in odd nuclei is explained. The theoretical results are compared to the available experimental data.