Low-lying dipole strength in exotic Ni isotopes
- Dr. Dominic Rossi, GSI, Darmstadt
Thursday, July 5, 11:00 AM - Special Seminar
NSCL Lecture Hall
The Pygmy Dipole Resonance (PDR) is a mode of nuclear excitation appearing at large neutron-to-proton imbalances in medium to heavy mass nuclei. Macroscopically, the PDR can be considered as an isospin-symmetric core oscillating against a shell of the remaining excess nucleons, in contrast to the well known Giant Dipole Resonance (GDR), in which the entire proton and neutron distributions oscillate against each other. Since the existence of this low-lying dipole mode is related to the neutron-proton asymmetry, the systematic investigation of the PDR contributes to the understanding of the nuclear equation-of-state.
Several experiments have been carried out in the past years using the R3B-LAND setup at GSI in Darmstadt, in which the electric dipole strength of exotic nuclei has been studied. The experimental method was based on heavy-ion-induced electromagnetic excitation and the subsequent particle and photon decay. Preliminary E1 strength distributions will be presented for neutron-rich Ni isotopes. In particular, the differential cross sections for the neutron-decay channels of 68Ni will be compared to other experimental data, obtained by virtual photon scattering. Preliminary data on the proton-decay channels of 32Ar and 34Ar will also be presented, for which a proton-related PDR has been predicted by an RPA calculation.