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Abstract: The ground-state structure of the near-drip-line nucleus 23O has been investigated in a one-neutron Coulomb breakup reaction. Differential cross sections for electromagnetic excitation of 23O projectiles (422 MeV/nucleon) incident on a lead target have been obtained from the measurement of the momenta of all breakup products including γ rays. The analysis of the deduced dipole-transition probability into the continuum infers a ground state configuration with a spectroscopic factor of 0.77(10) and thus a ground-state spin , resolving earlier conflicting experimental findings. Final-state interaction is of significant influence, an effective reduced scattering length for low-energy neutron scattering could be derived from the data. [Copyright &y& Elsevier]

Coulomb breakup of unstable neutron-rich carbon isotopes 15,17C has been studied at energies around ∼500–600 MeV/nucleon. Non-resonant low-lying dipole strength is observed in these isotopes which can be explained by a direct breakup mechanism. In addition to the decay neutron from excited projectile, γ-rays emitted from excited fragments after Coulomb breakup are measured in coincidence, giving access to quantitative spectroscopic information. The spectroscopic factor deduced for a valence neutron occupying the s1/2 level in the 15C ground state is consistent with that obtained earlier from (d,p) transfer reactions. The analysis for Coulomb breakup of 17C shows that most of the cross section yields the 16C core in excited states. The predominant ground-state configuration of 17C is found to be 16C(2+)⊗νs,d. [Copyright &y& Elsevier]

Coulomb break up of the neutron-rich 15,17C and 17–22O isotopes has been studied experimentally using secondary beams at energies of 500–600 MeV/u. A comparison between differential cross sections, dσ/dE*, with that obtained from a binary model shows that the main ground-state configuration of 15C is 14C(0+)⊗νS1/2 as expected. For 17C, our preliminary data analysis reveals that the predominant (∼64%) configuration of the ground state is 16C(2+)⊗νs,d. For 17–22O, the low-lying E1 strength amounts up to about 12% of the energy weighted sum rule strength depending on neutron number. The energy weighted E1 strength (integrated up to 15 MeV excitation energy) increases up to 20O then decreases for 21,22O. These data are compared to a shell model calculation. [Copyright &y& Elsevier]