Incomplete Energy Damping and Heavy-Residue Production in 197AU+86KR Collisions at E/A=35 MeV
The study of reactions between heavy nuclei at intermediate energies (E/A = 20–200 MeV) has attracted considerable experimental and theoretical interest. This intermediate-energy domain offers an opportunity to produce highly excited nuclear systems and to observe possibly the onset of new phenomena leading over to the high-energy regime, characterized by two-body nucleon-nucleon collisions. One of the phenomena that has attracted significant interest was the appearance of very slow (E/A ~ 0.1 — 0.5 MeV), heavy residues (HR) with masses comparable to that of the target. These HRs were observed in asymmetric systems, with several barns of cross section mostly concentrated at forward angles. The conditions for this process, the origin of the HRs, and the reason for their survival have not yet been well understood. A number of possible production mechanisms have been proposed,– such as fusion-like reactions (complete and incomplete fusion), fast fission, fragmentation, dissipative collisions, and even spallation. A dynamical retardation of the fission process has been considered as an explanation of the survival of the HRs. Hence, the process of HR production constitutes an important nuclear reaction mode which could possibly replace the fission mode at sufficiently high excitation energies. In the present work, ait exclusive 4π measurement of neutrons, light charged particles, and intermediate-mass products was performed in coincidence with projectile-like and target-like fragments (PLF and TLF), in order to determine the production mechanism of the HRs. The 197 Au+86 Kr reaction was studied at E/A = 35 MeV, since for this system, information on HRs was available from radiochemical measurements.
KeywordsCentral Collision Forward Angle High Excitation Energy Light Charged Particle Neutron Multiplicity
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