MULTIFRAGMENT EVENTS FROM HEAVY-ION COLLISIONS - SOURCES AND EXCITATION-FUNCTIONS

Multifragment events from 35, 40, 45, and 55 MeV/nucleon La-139 + C-12, Al-27, Ca-40, V-51, (nat)Cu, and La-139 reactions can be assigned to sources characterized by their velocity. At each bombarding energy, the probabilities of threefold, fourfold, and fivefold events increase substantially with decreasing source velocity, but are independent of the target mass. To remove the bombarding-energy dependence, a simple transformation has been applied which gives the excitation energy of the fused system in the simple incomplete-fusion picture. These "excitation functions" appear to be independent of both the system and bombarding energy.