Giant resonances in unstable oxygen isotopes

Electromagnetic and nuclear breakup of the neutron-rich Oxygen isotopes ran ging from A = 17 to A = 22 is studied experimentally in reactions at energi es 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 cros s sections d sigma/dE* for electromagnetic excitation, the EI-strength dist ributions can be deduced. For O-18,O-20,O-22, low-lying dipole strength is observed, exhausting about 5% of the Thomas Reiche Kuhn sumrule for energie s up to 5 MeV above the continuum threshold.