Study of the mechanism of 16O-induced reactions between 140 and 315 MeV incident energies

Reactions induced by 16O ions on 238U at incident energies of E/A = 20 MeV have been studied. In coincidence with fission fragments, projectile residues (Li,...,O) have been measured near the grazing angle and double differential cross sections have been measured for energetic p,d,t, and α-particles. The folding-angle between the two coincident fission fragments is shown to provide information on the linear momentum transfer to the target nucleus. The emission of energetic light particles into the forward direction is shown to be an important aspect of the mechanism of projectile residue emission. However, light particles emitted in coincidence with projectile residues are not the result of a simple quasi-elastic breakup of the projectile. This is shown by a kinematical analysis which demonstrates that a large amount of linear momentum is transferred to the target residue prior to fission. Double differential cross sections have also been measured for energetic p,d,t, and α-particles emitted in 16O-induced reactions on targets of Al, Zr, and Au at incident energies of 140, 215, and 310 MeV. The energy and angular distributions are well described by isotropic emission from a moving thermal source. The extracted temperature and velocity parameters are found to vary systematically with the incident energy per nucleon above the Coulomb barrier. The observed trend cannot be explained by compound nucleus emission but instead suggest emission from a source which consists of comparable contributions from target and projectile. Alternatively, the proton energy spectra are compared with a rotation hot spot model, a precompound model, and with a simple knock-out model