| Complex fragment emission has been studied in the 60 MeV/A {dollar}sp{lcub}197{rcub}{dollar}Au + {dollar}sp{lcub}12{rcub}{dollar}C, {dollar}sp{lcub}27{rcub}{dollar}Al, {dollar}sp{lcub}51{rcub}{dollar}V, {dollar}sp{lcub}rm nat{rcub}{dollar}Cu, and {dollar}sp{lcub}197{rcub}{dollar}Au reactions. Velocity spectra, angular distributions and cross sections have been constructed for each target from the inclusive data. Coincidence data including 2-, 3-, 4-, and 5-fold events have also been examined.; In the 60 MeV/A {dollar}sp{lcub}197{rcub}{dollar}Au + {dollar}sp{lcub}12{rcub}{dollar}C reactions, the complex fragments are produced mainly in highly equilibrated binary processes; in particular, they arise from the compound binary decay of Au-like nuclei. The relaxed nature of the decay process has been determined by the angular distributions and emission velocities of the fragments. The binary nature of the decay process has been illustrated by the well defined Coulomb rings and by the 2-fold coincidence events. Higher n-fold events (n = 3, and 4) have also been observed but are less than 2% of the total coincidence events.; In the 60 MeV/A {dollar}sp{lcub}197{rcub}{dollar}Au + {dollar}sp{lcub}27{rcub}{dollar}Al, {dollar}sp{lcub}51{rcub}{dollar}V, {dollar}sp{lcub}63{rcub}{dollar}Cu, and {dollar}sp{lcub}197{rcub}{dollar}Au reactions the flat angular distributions of the fragments along with their Coulomb like emission velocities suggest the presence of a strong compound binary component in the inclusive data. This component is associated with the compound nucleus decay of Au-like projectiles generated in peripheral collisions and dominates the singles cross-sections. However, in these reactions a significant yield of fragments arises also from multifragmentation.; The neutron multiplicity is utilized in the present experiment as an independent measure of the deposited excitation energy; in peripheral reactions one observes low neutron multiplicities associated with low excitation energies, while the more central collisions are associated with high neutron multiplicities and high excitation energies.; Possible mechanisms for multifragmentation are investigated by comparing some theories with the experimental data. The 60 MeV/A Au-induced reactions are simulated by coupling a kinetic description of the dynamical stage of the collision with a subsequent statistical decay of the primary sources. Results obtained with this model are shown and are compared with both inclusive and exclusive experimental data.; In a different approach, the possibility that the system undergoes a phase transition (percolation-like or liquid vapor-like) is investigated by examining observables that behave qualitatively differently whether a phase transition is present or not.; Finally a characteristic energy dependence of the multifragment decay probabilities of the source or sources is presented similar to that observed for fission probabilities at low energies. This behavior seems to relegate the role of dynamics to the formation of the sources, which then proceed to decay in an apparently statistical manner. (Abstract shortened by UMI.)... |
