  We have calculated the electric dipole strength distributions in the unstable
neutron rich oxygen isotopes $^{18,20,22}$O, in a model which include up to
four quasi-particle-type configurations. The model is the extension, to include
the effect of the pairing correlations, of a previous model very successful
around closed shell nuclei, and it is based on the quasi-particle-phonon
coupling. Low-lying dipole strength is found, which exhausts between 5 and 10%
of the Thomas-Reiche-Kuhn (TRK) energy-weighted-sum-rule (EWSR) below 15 MeV
excitation energy, in rather good agreement with recent experimental data. The
role of the phonon coupling is shown to be crucial in order to obtain this
result.
