Multifragment events from 35, 40, 45, and 55 MeV/nucleon ${}_{}{}^{139}{}_{}{}^{}\mathrm{La}$${+}^{12}$C, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}$, ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Cu}$, and ${}_{}{}^{139}{}_{}{}^{}\mathrm{La}$ 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 independent of both the system and bombarding energy.

• Received 18 December 1990

DOI:https://doi.org/10.1103/PhysRevLett.66.576