Continuum shell-model investigation of the photoexcited giant quadrupole resonance in 16O

The photoexcited giant quadrupole resonance in 16O has been investigated by the anisotropy of the angular distribution of differential cross sections. The analysis uses the continuum shell-model in the formulation given elsewhere within the framework of the 1p-1h model. The anisotropy coefficients and energy dependences of the partial cross sections have been calculated and are compared with the data available at Esub(γ)=10-30 MeV. A good agreement is stated. But the resonance structure is not satisfactorily reproduced. The conclusion is drawn that the broad distribution of quadrupole strength experimentally observed near 24 MeV excitation energy can be explained by including more complicated configurations (such as 2p-2h) in the model