Ju l 2 00 6 Production of cold fragments in nucleus - nucleus collisions in the Fermi - energy domain

The reaction mechanism of nucleus-nucleus collisions at projectile energies around the Fermi energy is investigated with emphasis on the production of fragmentation-like residues. The results of simulations are compared to experimental mass distributions of elements with Z = 21-29 observed in the reactions 86 Kr+ 124,112 Sn at 25 AMeV. The model of incomplete fusion is modified and a component of excitation energy of the cold fragment dependent on isospin asymmetry is introduced. The modifications in the model of incomplete fusion appear consistent with both overall model framework and available experimental data. A prediction is provided for the production of very neutron-rich nuclei using a secondary beam of 132 Sn where e.g. the 1 reaction 132 Sn+ 238 U at 28 AMeV appears as a possible alternative to the use of fragmentation reactions at higher energies.