  The properties of the low-lying, collective 2+ states in neutron-rich oxygen
isotopes are investigated in the framework of self-consistent microscopic
models with effective Skyrme interactions. In RPA the excitation energies E2+
can be well described but the transition probabilities are much too small as
compared to experiment. Pairing correlations are then accounted for by
performing quasiparticle RPA calculations. This improves considerably the
predictions of B(E2) values and it enables one to calculate more reliably the
ratios Mn/Mp of neutron-to-proton transition amplitudes. A satisfactory
agreement with the existing experimental values of Mn/Mp is obtained.
