Complete fusion or residue distributions have been measured with several experimental techniques for the following systems: ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$+ ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$+ ${}_{}{}^{24,26}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$+ ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{28,29,30}{}_{}{}^{}\mathrm{Si}$. The range of energies spreads from 1 to 3 times the Coulomb barrier. None of these systems presents structures in its fusion excitation function as pronounced as the ones observed for lighter entrance channels. The intensities of the residue distribution are generally in agreement with the predictions of a multiple deexcitation code. The shape and absolute values of complete fusion excitation functions are compared to macroscopic models and to the predictions of a coupled-channels approach of the reaction, which gives a more satisfactory account of experimental data.

NUCLEAR REACTIONS Fusion, measured ${\sigma }_{\mathrm{fusion}}(E,\theta )$, ${\sigma }_{\mathrm{residue}}(E,\theta )$; ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$+ ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, $16.4<\mathrm{}{E}_{\mathrm{c}.\mathrm{m}.\mathrm{}}<29.8\mathrm{}$ MeV; ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$+ ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, $15.1<\mathrm{}{E}_{\mathrm{c}.\mathrm{m}.\mathrm{}}<24.6\mathrm{}$ MeV; ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$+ ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, $21<\mathrm{}{E}_{\mathrm{c}.\mathrm{m}.\mathrm{}}<41.6\mathrm{}$ MeV; ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$+ ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$, $20.3<\mathrm{}{E}_{\mathrm{c}.\mathrm{m}.\mathrm{}}<32.9\mathrm{}$ MeV; ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$+ ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, $24.2<\mathrm{}{E}_{\mathrm{c}.\mathrm{m}.\mathrm{}}<38.1\mathrm{}$ MeV; ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$+ ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, $27.9<\mathrm{}{E}_{\mathrm{c}.\mathrm{m}.\mathrm{}}<41.4\mathrm{}$ MeV; ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$+ ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$, $27.4<\mathrm{}{E}_{\mathrm{c}.\mathrm{m}.\mathrm{}}<42.1\mathrm{}$ MeV; ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$+ ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$, $27.3<\mathrm{}{E}_{\mathrm{c}.\mathrm{m}.\mathrm{}}<42.8\mathrm{}$ MeV; comparison with evaporation calculation; barrier parameters deduced from ${\sigma }_{\mathrm{CF}}\mathrm{}\left(E\right)\mathrm{}$. Comparison of ${\sigma }_{\mathrm{CF}}\mathrm{}\left(E\right)\mathrm{}$ with macroscopic models; coupled-channels approach of the fusion strength.

• Received 27 July 1981

DOI:https://doi.org/10.1103/PhysRevC.25.1877