Sequential fissions of heavy nuclear systems
By D. Gruyer - GANIL (séminar in french!)
In 129 Xe+nat Sn reactions from 8 to 20 MeV/A, measured with the 4π INDRA multidetector, the three-fragment exit channel occurs with a significant cross section. In this work, we show that these fragments arise from two successive binary splittings. Using event by event kinematic correlations, the sequence of fragment production is determined. The two steps are then reconstructed. They are identified as fission-like mechanisms, indicating that a heavy nuclear system is formed. For the higher beam energies, strong Coulomb proximity effects are observed in the three-fragment final state. By comparison with Coulomb trajectory calculations, we show that the time scale between the consecutive scission steps decreases with increasing bombarding energy. Finally, investigation of the three-fragment exit channel in the reaction 129 Xe+197 Au at 15 MeV/A indicates the formation of heavy systems with atomic number greater than Z = 100.