Coulomb chronometry to probe the decay mechanism of hot nuclei

Diego Gruyer, J D. Frankland, Eric Bonnet, A Chbihi, G Ademard, M Boisjoli, B Borderie, R Bougault, E Galichet, J Gauthier, D Guinet, P Lautesse, N Le Neindre, E Legouée, I Lombardo, O Lopez, L Manduci, P Marini, K Mazurek, P. Nadtochy, M Pârlog, M. F. Rivet, R. Roy, E Rosato, G Spadaccini, G Verde, E Vient, M Vigilante, J. P. Wieleczko

Published 2013-09-30, updated 2015-11-19Version 4

In 129 Xe+ nat Sn central collisions from 8 to 25 MeV/A, the three-fragment exit channel occurs with a significant cross section. We show that these fragments arise from two successive binary splittings of a heavy composite system. The sequence of fragment production is determined. Strong Coulomb proximity effects are observed in the three-fragment final state. A comparison with Coulomb trajec-tory calculations shows that the time scale between the consecutive break-ups decreases with increasing bombarding energy, becoming quasi-simultaneous above excitation energy E * = 4.0$\pm$0.5 MeV/A. This transition from sequential to simultaneous break-up was interpreted as the signature of the onset of multifragmentation for the three-fragment exit channel in this system.