Exclusive studies of 130-270 MeV 3He- and 200-MeV proton-induced reactions on 27Al, natAg, and 197Au

Exclusive light-charged-particle and IMF spectra have been measured with the ISiS detector array for bombardments of Al-27, Ag-nat, and Au-197 nuclei with 130-270-MeV He-3 and 200-MeV protons. The results are consistent with previous interpretations based on inclusive data that describe the global yield of complex fragments in terms of a time-dependent process. The emission mechanism for energetic nonequilibrium fragments observed at forward angles with momenta up to twice the beam momentum is also investigated. This poorly understood mechanism, for which the angular distributions indicate formation on a time scale comparable to the nuclear transit time, are accompanied primarily by thermal-like emissions. The data are most consistent with a schematic picture in which nonequilibrium fragments are formed in a localized region of the target nucleus at an early stage in the energy-dissipation process, where the combined effects of high energy density and Fermi motion produce the observed suprathermal spectra.