Elastic scattering of the proton drip line nuclei Be7,B8, and C9 on a lead target at energies around three times the Coulomb barriers

Elastic scattering angular distributions of the proton drip line nucleus, C-9, impinging on a Pb-nat target have been measured for the first time at energies around three times the Coulomb barriers at the Radioactive Ion Beam Line in Lanzhou. The same measurements were made for B-8 and Be-7 simultaneously. The measured elastic scattering angular distribution of 9C on a lead target does not show any particular reduction at around the Coulomb rainbow angles, suggesting that the breakup coupling effect on the elastic scattering channel is very small in this energy region. A similar observation is made for 8B. Analysis with the continuum discretized coupled channels (CDCC) method shows that it is the Coulomb and/or the centrifugal barriers exerted on the valence protons that counteract the breakup coupling effects on the elastic scattering channel. CDCC calculations assuming C-9 to have a Be-7 + 2p cluster structure give elastic scattering cross sections similar to those for a B-8 + p structure. The calculated breakup cross sections with these two assumed structures of C-9 differ quite a bit at around the Coulomb rainbow angles, suggesting that the breakup cross sections, instead of the elastic scattering ones, are more sensitive to the structure of proton-rich nuclei at incident energies around three times the Coulomb barriers.