ar X iv : n uc l - ex / 0 11 00 15 v 1 2 5 O ct 2 00 1 Heavy Residue Formation in 20 MeV / nucleon 197 Au + 90 Zr Collisions

The yields and velocity distributions of heavy residues and fission fragments from the reaction of 20 MeV/nucleon 197 Au + 90 Zr have been measured using the MSU A1200 fragment separator. A bimodal distribution of residues is observed, with one group, resulting from peripheral collisions, having fragment mass numbers A=160– 200 while the other group, resulting from " hard " collisions, has A=120–160. This latter group of residues can be distinguished from fission fragments by their lower velocities. A model combining deep-inelastic transfer and incomplete fusion for the primary interaction stage and a statistical evaporation code for the deexcitation stage has been used to describe the properties of the product distributions.