Experimental evidence of primary emission of light particles from compound nuclei prior to fission, 3-body or many-body breakup

Abstract : Collisions of Xe+Sn at energy range of E/A = 8 to 30 MeV and leading to fusion-like heavy residues are studied using the 4π INDRA multidetector. The energy spectra of light charged particles (LCP) in coincidence with one-, 2- or many-body residues have been analyzed. It reveals that a composed system is formed, it is highly excited and first decays by emitting LCP's and then may breakup into 2- or many- fragments or survives as an evaporative residue. A quantitative estimation of this primary emission is given and compared to the secondary decay of the fragments. These analysis indicate that most of evaporative LCP precedes not only fission but also precedes breakup into several fragments. This founding put hard constraints on dynamical and statistical multifrgamentation models.