Particle-core coupling around (68)Ni: a study of the subshell closure at N = 40

We investigate the Coulomb dissociation of 8B on a (208) Pb target at the beam energy of 250 MeV/nucleon. employing the cross sections for the radiative capture reaction Be(p,(gamma)) B calculated within the Shell Model Embedded in the Continuum (SMEC) approach. In contrast to the situation at lower beam energies, the Coulomb breakup cross sections are found to be sensitive to the MI transitions. Comparisons of SMEC and single-particle potential model predictions show that the Coulomb breakup cross sections at these high energies are sensitive to the structure model of 8B. Comparison with the preliminary data on the angle integrated spectra reported recently by the GSI group shows that the theory is able to reproduce the absolute magnitude as well as the shape of this data well. The contributions of the E2 component strongly depends on the range of the angles of the p-7Be center of mass with respect to the beam direction, included in the angular integrations of the double differential cross section. If integrations are done over the angular range of 0°-1.87°, the E2 multipolarity contributes up to 25 % to the cross sections even for the relative energies of [p- Be] below 0.25 MeV. However, these contributions are reduced by an order of magnitude at lower relative energies if the maximum of the angle integration is ~ 1°.