An analysis of neutron and proton scattering off 40,48 Ca has been carried out. Real and imaginary potentials have been generated using the Nuclear Structure Method for scattering with the Gogny D1S nucleon-nucleon effective interaction. Observables are well described by NSM for neutron and proton elastic scattering off 40 Ca and for neutron scattering off 48 Ca. For proton scattering off 48 Ca, NSM yields a lack of absorption. This discrepancy is attributed to double-charge-exchange contribution and coupling to Gamow-Teller mode which are not included in the present version of NSM. A recipe based on a Perey-Buck fit of NSM imaginary potential and Lane model is proposed to overcome this issue in an approximate way. PACS. PACS-key describing text of that key-PACS-key describing text of that key

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We call projectile fragmentation of neutron halo nuclei the elastic breakup (diffraction) reaction, when the observable studied is the neutron-core relative energy spectrum. This observable has been measured in relation to the Coulomb breakup on heavy target and recently also on light targets. Such data enlighten the effect of the neutron final state interaction with the core of origin. Projectile fragmentation is studied here by a time dependent model for the excitation of a nucleon from a bound state to a continuum resonant state in a neutron-core complex potential which acts as a final state interaction. The final state is described by an optical model S-matrix so that both resonant and non resonant states of any continuum energy can be studied as well as deeply bound initial states. It turns out that due to the coupling between the initial and final states, the neutron-core free particle phase shifts are modified, in the exit channel, by an additional phase. Some typical numerical calculations for the relevant observables are presented and compared to experimental data. It is suggest that the excitation energy spectra of an unbound nucleus might reflect the structure of the parent nucleus from whose fragmentation they are obtained.