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

The Ni-58 + Ni-58 reaction at 30 MeV/nucleon has been experimentally investigated at the Superconducting Cyclotron of the INFN Laboratori Nazionali del Sud. In midperipheral collisions the production of massive fragments (4 less than or equal to Z less than or equal to 12), consistent with the statistical fragmentation of the projectile-like residue and the dynamical formation of a neck, joining projectile-like and target-like residues, has been observed. The fragments coming from these different processes differ both in charge distribution and isotopic composition. In particular it is shown that these mechanisms leading to fragment production act contemporarily inside the same event.