The influence of fission on the fragmentation of relativistic 208Pb and 238U projectiles in peripheral collisions

Abstract The projectile fragmentation in peripheral nuclear collisions was studied using ≈ 1 GeV·A of 208 Pb and 238 U from the SIS at GSI, impinging on a copper target. Lead and thallium isotopes from the fragmentation of 208 Pb as well as uranium and protactinium isotopes from 238 U, were selected by the fragment separator FRS. In contrast to the fragmentation of 208 Pb, the cross sections for the production of heavy fragments from 238 U are strongly reduced by fission. The measured isotopic yields may be explained quantitatively by calculations in the framework of the abrasion-ablation model, if fission is allowed to compete with particle evaporation in the deexcitation of the prefragments.