Isospin Effect of Fragmentation Reaction on the Isotopic Distribution Produced in Intermediate Energy Heavy Ion Collisions

Fragments produced in the reaction of 60 MeV/n ¹⁸O on Be have been measured experimentally. The isotopic distribution of fragmentation reaction is well reproduced by a modified statistical abrasion-ablation model. It is predicted that the isotopic distribution shifts toward the neutron rich side for neutron rich projectile, but this isospin effect decreases with the increase 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 projectile respectively.