Spectroscopy of light exotic nuclei using nuclear break‐up

One‐nucleon removal reactions at relativistic energies have been used as spectroscopic tool to obtain information about the ground state properties of several neutron‐rich isotopes in the sd‐shell. Using the FRS at GSI, the longitudinal momentum distributions of the emerging fragments after one‐nucleon removal cross‐sections were measured. The relative contributions of the remaining fragments in their ground and excited states have been determined from measurements of γ rays in coincidence with the longitudinal momentum distributions. The interesting case of 23O will be directly address. The interpretation of our experimental results in the framework of a simple theoretical model will favours a spin and parity assignment of 1/2+ for the 23O ground state in agreement with shell model predictions.