BREAKUP OF THE PROJECTILE IN O-16-INDUCED REACTIONS ON AL-27, NI-58, AND AU-197 TARGETS AROUND 100 MEV/NUCLEON

The spatial correlation among the four He ions coming from the disassembly of the O-16 projectile on Al-27, Ni-58, and Au-197 targets has been studied at 94 MeV/nucleon. Charged particles have been detected by a multielement array of plastic scintillators covering the angular domain between 3-degrees and 150-degrees. Standard relativistic kinematics has been used to reconstruct the excitation energy of the primary projectile-like nucleus (E(PLN)*). Mean values of this quantity are found independent of the target mass and the comparison with existing similar data taken at lower bombarding energies shows a saturation of E(PLN)* around 3 MeV/nucleon. An event-by-event analysis has been performed in order to study the distributions of some global variables such as coplanarity, sphericity, and relative angle, helpful in the understanding of the topological characteristics of the process and in the evaluation of its time scale. Experimental-data have also been compared with the results of Monte Carlo simulations based on different reaction mechanisms and it is possible to conclude that sequential emission of the fragments is preferred.