Dipole strength function in ²⁰O

The dipole strength function of neutron-rich ²⁰O was measured in the region of 1 to 8 MeV by the method of virtual photon scattering. This method relies on the detection of real decay-photons following the virtual excitation of relativistic projectiles. A 100 MeV/u ²⁰O beam was excited by a ²⁰⁸Pb target and the energy-loss of the projectile was correlated with the γ-ray energies. The observed ²⁰O excitation spectrum shows several broad peaks in the region above 3 MeV, which indicates a shifting of low-lying dipole strength from higher excitation energies in this neutron-rich oxygen isotope.