Particle-particle coincidence measurements for 1,2,3H and He4 in the reaction 480 MeV Ag56

Particle-particle coincidence measurements have been made between light charged particles (1,2,3H and He4) produced in the reaction (8.5 MeV/nucleon) 56Fe+natAg. This coincidence requirement emphasizes central collisions leading to evaporation residues. Average multiplicities are found to be approximately three alphas and approximately four protons per evaporation residue; these values imply that approximately (1/2 the initial excitation energy of about 211 MeV is evacuated from the evaporation residues by these particles. This fractional energy evacuation by charged particles is considerably larger than that found for the similar reaction (8.5 MeV/nucleon) Ag40. In both reactions the effective emission barriers for H1 and He4 (as deduced from the energy spectra) are found to be significantly lower than corresponding empirical fusion barriers between cold nuclei. This is particularly surprising for emitter nuclei that survive fission.