Electromagnetic Excitation of Neutron-Rich Oxygen Nuclei 17-22O

The dipole response of neutron-rich oxygen nuclei ^17-22O has been studied using the electromagnetic excitation process in heavy ion collisions at beam energies around 600 MeV/nucleon. The subsequent neutron decay after inelastic scattering of the secondary beam projectiles on a Pb target was measured in a kinematically complete experiment. Differential electromagnetic excitation cross sections were deduced up to 30 MeV excitation energy. For all isotopes low-lying E1 strength was obtained exhausting between 5% and 12% of the energy-weighted dipole sum rule.