SPECTRAL-LINE SHAPE OF EXOTIC NUCLEI

The quadrupole strength function of O-28 is calculated making use of t he SIII interaction, within the framework of continuum-RPA and taking into account collisions among the nucleons (doorway coupling). The cen troid of the giant resonance is predicted at approximate to 14 MeV, wh ich is much below the energy expected for both isoscalar and isovector quadrupole resonances in nuclei along the stability valley. About hal f of its width arises from the coupling of the resonance to the contin uum and about half is due to doorway coupling. This result is similar to that obtained in the study of giant resonances in light, beta-stabl e nuclei, and shows the lack of basis for the expectation, entertained until now in the literature, that continuum decay was the main dampin g mechanism of giant resonances in halo nuclei.