Contemporary presence of dynamical and statistical production of intermediate mass fragments in midperipheral Ni-58+Ni-58 collisions at 30 MeV/nucleon

The Ni-58 + Ni-58 reaction at 30 MeV/nucleon has been experimentally invest igated at the Superconducting Cyclotron of the INFN Laboratori Nazionali de l Sud. In midperipheral collisions the production of massive fragments (4 l ess than or equal to Z less than or equal to 12), consistent with the stati stical fragmentation of the projectile-like residue and the dynamical forma tion of a neck, joining projectile-like and target-like residues, has been observed. The fragments coming from these different processes differ both i n charge distribution and isotopic composition. In particular it is shown t hat these mechanisms leading to fragment production act contemporarily insi de the same event. (C) 2001 Elsevier Science B.V. All rights reserved.