Isospin effect of fragmentation reaction on the isotopic distribution produced in intermediate energy heavy ion collisions

Fragments produced in the reaction of 60MeV/n O-18 On Be have been measured experimentally. The isotopic distribution of fragmentation reaction is wel l reproduced by a modified statistical abrasion-ablation model. It is predi cted that the isotopic distribution shifts toward the neutron rich side for neutron rich projectile, but this isospin effect decreases with the increa se of the atomic number difference Z - Z(A) and disappears at last, where Z and Z(A) are atomic numbers of the isotopic distribution and the projectil e respectively.