COULOMB DISSOCIATION OF LI-11 AND BE-11 IN A DIRECT FRAGMENTATION MODEL

The Coulomb dissociation contribution to the two-neutron and one-neutron removal cross section of, respectively, Li-11 and Be-11 projectiles has been calculated in a direct fragmentation model. The model is formulated within the framework of the post form distorted-wave Born approximation. In this theory, the "post acceleration effect" of the Li-9 and Be-10 fragments in the final channel is accounted for properly. The Coulomb break-up can explain approximately upto 80% of the experimental 2n removal cross section of Li-11 for the Au-197 target at the incident energy of 29 MeV/A. The beam energy dependence of the calculated cross sections is in good agreement with the few experimental points presently available. The angular distributions of the Li-9 as well as of 2n system are found to be concentrated in the very forward angles.