Measurement of the dipole response of neutron-rich nuclei in the A∼20 region

Abstract

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 +)⊗ ν S 1/2 as expected. For 17C, our preliminary data analysis reveals that the predominant (∼64%) configuration of the ground state is 16C(2 +)⊗ ν s, 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.