Mechanisms for light charged particle emission in the reactions 247 and 337 MeV Ar40+natAg

Light charged particles from the reactions 247 and 337 MeV Ar40+natAg have been measured in singles and in coincidence with fission-like products. Most of the H1 and He4 in coincidence with fusion-fission and quasifission can be accounted for by evaporation from the composite nucleus or by the fragments. Multiplicities are determined for H1 and He4 in association with evaporation residues, fusion-fission, and quasifission. The probability for composite nucleus emission decreases with increasing spin zone of the emitter and gives a view of the role of emitter lifetime. The ratio of composite-nucleus multiplicities for quasifission/fusion-fission is about 1/2 ((1/4) for 337 MeV Ar40 (247 MeV Ar40) which implies a similar ratio for the lifetimes of the respective composite nuclei between thermalization and scission. Energy spectra and angular distributions of particles (in coincidence with fusion-fission and quasifission) are consistent with emission from a strongly distorted nuclear system en route toward scission. Prethermalization emission of He4 is observed at 10°in comparable amounts for peripheral collisions (quasifission and fusion-fission) and for central collisions.