S. Wan

Giant resonances in unstable oxygen isotopes

Abstract Electromagnetic and nuclear breakup of the neutron-rich Oxygen isotopes ranging from A = 17 to A = 22 is studied experimentally in reactions at energies around 600 MeV/u. The beams were produced in fragmentation reactions and separated by the GSI Fragment Separator FRS. By measuring the four-momenta of all decay products after inelastic scattering and neutron decay of the projectile, the excitation energy is determined. From the differential cross sections dσ dE ∗ for electromagnetic excitation, the E1-strength distributions can be deduced. For 18,20,22 O, low-lying dipole strength is observed, exhausting about 5% of the Thomas Reiche Kuhn sumrule for energies up to 5 MeV above the continuum threshold.

Continuum excitations in neutron-rich Oxygen isotopes

Electromagnetic and nuclear excitations of the neutron-rich Oxygen isotopes ranging from A=17 to A=22 are studied experimentally in reactions at energies around 600 MeV/u. By measuring the four-momenta of all decay products the excitation energy is determined. From the differential cross sections for electromagnetic excitation, the E1-strength distributions can be deduced. For 18,20,22O, low-lying dipole strength is observed, exhausting about 5% of the energy weighted TRK sumrule for energies up to 5 MeV above the continuum threshold.

New Results On 8B And 23O Ground State Properties

One‐nucleon removal reactions at relativistic energies have been used as spectroscopic tool to obtain information about the ground state properties of 8B and 23O. Using the FRS at GSI, the longitudinal momentum distributions of the emerging fragments after breakup and the one‐nucleon removal cross‐sections were measured. The relative contributions of the remaining fragments (7Be and 22O) in their ground and excited states have been determined from measurements of γ rays in coincidence with the longitudinal momentum distributions. In the 8B case, the experimental breakup data on two different targets (C and Pb) allow a determination of the weight of the 7Be* component in the 8B ground state wave function as (13.3±2.2) %. These results are discussed in the context of a theoretical three‐body model. Preliminary results on 23O indicate a spin and parity assignment of 1/2+ in agreement with shell model predictions.