FUSION-LIKE REACTIONS OF AR-40 UP TO 1.36 GEV - PRETHERMALIZATION ANDPOSTTHERMALIZATION PARTICLES AND FRAGMENTS

Heavy residual nuclei are shown to result from the most violent (i.e., central) collisions for Ar-40 + Ag reactions of up to 1.36 GeV; their average velocities are greater than or similar to 80% of the c.m. vel ocity. Angular and energy distributions for H-1,H-2,H-3, He-3,He-4, an d Li are measured in coincidence with these heavy nuclei. The dominant light particle components are nearly isotropic in a frame of referenc e having the velocity of the heavy residues. In addition there are for ward-peaked high-energy components of the H, He, and Li emission attri butable to prethermalization emission. Fractional abundances of these prethermalization components increase markedly with increasing inciden t energy. Mass and momentum balance preclude the presence of a project ilelike fragment and thus indicate fusionlike reactions with large but incomplete linear momentum transfer. The remainder of the momentum is carried away by the spray of forward-peaked ejectiles. For 1.36 GeV A r-40 similar to 1/2 of the 900 MeV available is completely thermalized , and similar to 1/2 goes into prethermalization emission after strong collisional mixing.