LOW-ENERGY ELECTRIC-DIPOLE MODES IN NUCLEI AROUND N = 82

Nuclear Resonance Fluorescence experiments have been performed on sphe rical nuclei around neutron number N=82. Detailed information on energ ies, cross sections and absolute transition strengths (i.e. lifetimes) of dipole excitations between 1 and 4 MeV have been obtained for the nuclei Pr-141, Nd-142 and Nd-143. A very strongly excited 1--state in Nd-142 at 3.425 MeV is assigned as a member of the two-phonon 2+ x 3-- multiplet. Calculations in the framework of the sdf-Interacting Boson Model for a similar state in the N=82 nucleus 144Sm confirm this assum ption. In the neighbouring odd A nuclei Pr-141 and Nd-143 we found fir st evidence for the existence of two-phonon-particle-states which appe ar due to the coupling of the unpaired nucleon with the members of the 2+ x 3--multiplet in the core nucleus.