Fusion evaporation-residue cross sections for 28Si+40Ca at E(28Si)=309, 397, and 452 MeV.

Velocity distributions of mass-identified evaporation residues produced in the {sup 28}Si+{sup 40}Ca reaction have been measured at bombarding energies of 309, 397, and 452 MeV using time-of-flight techniques. These distributions were used to identify evaporation residues and to separate the complete-fusion and incomplete-fusion components. Angular distributions and upper limits for the total evaporation-residue and complete-fusion evaporation-residue cross sections were extracted at all three bombarding energies. The complete-fusion evaporation-residue cross sections and the deduced critical angular momenta are compared with earlier measurements and the predictions of existing models. The ratios of the complete-fusion evaporation-residue cross section to the total evaporation-residue cross section, along with those measured for the {sup 28}Si+{sup 12}C and {sup 28}Si+{sup 28}Si systems at the same energies, support the entrance-channel mass-asymmetry dependence of the incomplete-fusion evaporation-residue process reported earlier.