Incomplete fusion and cluster production in heavy-ion collisions at 30 MeV/nucleon

The total energy dissipated in central collisions has been measured for the system S32+58Ni at about 1 GeV incident energy. An event-by-event reconstruction of the atomic charge of the reaction products was performed by means of a 4 charged-particle detector. Two distinct classes of events were thus separated: one consistent with a conventional incomplete fusion-evaporation process; a second where three or more heavy fragments are produced. A subtraction of the evaporative component from the particle spectra at all angles allowed extraction of the excitation energy removed from the system by pre-equilibrium emission. The average excitation energies corresponding to the two different classes of events were determined. Comparisons with statistical model calculations as well as a multifragmentation model are presented.