Coulomb and nuclear effects in the fragmentation of exotic nuclei

Abstract

The role of the nuclear and the Coulomb interactions in the dissociation of the neutron-rich exotic nuclei 11Li, 11Be and 14Be incident on a number of targets has been studied. The two-neutron removal cross sections of 11Li and 14Be and one-neutron removal cross section of 11Be have been calculated. The theory of diffraction dissociation and diffraction stripping has been used to account for the nuclear effects. The Coulomb-dissociation cross sections have been calculated within the framework of a direct fragmentation model formulated earlier. The Coulomb dissociation along with the nuclear cross sections explain satisfactorily the target-mass dependence of the experimental total two-neutron removal cross sections of 11Li and 14Be around 30 MeV/ A incident energy. The beam-energy dependence of this cross section is also well reproduced. The stripping contributions dominate the nuclear cross sections. The dependence of the reaction mechanism underlying the two-neutron removal process on the separation energy of the two-neutron system in the projectile is discussed. The role of the “post-acceleration effect” on the energy spectra of the produced fragments is investigated.