Study of the reactions occurring in the fusion of 12C and 16O with heavy nuclei at incident energies below 10 MeV/nucleon

The excitation functions for production of many residues in the fusion of C12 with Ta181 and Au197 and of O16 with Ho165 and Ta181 have been measured at incident energies varying from the Coulomb barrier up to about 10 MeV/nucleon. The cross sections for fusion of these ions without fission have been deduced and they show that such a process may only occur for projectile angular momenta smaller than a critical value. The excitation functions for individual reactions provide evidence for the emission of preequilibrium nucleons during the thermalization of the composite nucleus and may be satisfactorily reproduced by a calculation based on the Boltzmann master equation theory