Velocity and angular distributions of evaporation residues from 32S-induced reactions.

Abstract

Velocity distributions of mass-resolved evaporation residues from reactions of $^{32}\mathrm{S}$ with $^{12}\mathrm{C}$, $^{24}\mathrm{Mg}$, $^{27}\mathrm{Al}$, $^{28}\mathrm{Si}$, and $^{40}\mathrm{Ca}$ have been measured at bombarding energies of 194, 239, and 278 MeV using time-of-flight techniques. In all cases, the observed shifts in the velocity centroids relative to the values expected for complete fusion are consistent with a previously reported parametrization of a threshold for onset of incomplete fusion. Angular distributions were measured and total cross sections extracted for the $^{32}\mathrm{Mg}$ system at all three energies. A comparison with existing results for $^{32}\mathrm{Mg}$ at lower energies, and with other systems leading to the $^{56}\mathrm{Ni}$ compound nucleus, suggests two different types of compound-nuclear limitations to complete fusion at higher energies.