title: Mode coupling and the pygmy dipole resonance in a relativistic two-phonon model.
abstract: A new class of many-body models, based on covariant density functional theory for excited states, is presented. It allows a parameter free description of the fragmentation of nuclear states induced by mode coupling of two-quasiparticle and two-phonon configurations. As compared to earlier methods it provides a consistent and parameter free theory of the fine structure of nuclear resonances. The method is applied very successfully to investigate the newly discovered low-lying dipole excitations in Sn and Ni isotopes with large neutron excess.
authors.affiliation: GSI Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt, Germany and Institut für Theoretische Physik, Goethe-Universität, 60438 Frankfurt am Main, Germany and Institute of Physics and Power Engineering, 249033 Obninsk, Russia.
authors.forename: Elena
authors.initials: E
authors.lastname: Litvinova
authors.forename: Peter
authors.initials: P
authors.lastname: Ring
authors.forename: Victor
authors.initials: V
authors.lastname: Tselyaev