Emission Time And Sequence In A Ni-58+C-12 Fusionlike Source At 34.5 Mev/Nucleon

Fusionlike events in Ni-58+C-12 at 34.5 MeV/nucleon are isolated by use of the statistical discriminant analysis method applied to a set of 20 global variables in complete events with at least 90% of the total charge of the system. Two-fragment reduced-velocity correlation functions are measured for the emission of intermediate mass fragments (IMF's) and compared to many-body trajectory calculations. Alpha particle emission sequence has been deduced as a function of excitation energy. At the highest excitations, alpha particles are emitted simultaneously with IMF's on a time scale of about 200-300 fm/c. In less excited events, they are emitted on a longer time scale. This hybrid deexcitation mechanism, sequential and prompt, is corroborated by comparing the charge of the heaviest and the second heaviest fragments to predictions of GEMINI and SMM simulations.