The excitation function for production of evaporation residues from the fusion of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ has been studied in two experiments. In the first experiment the $\gamma$-ray yields of transitions populating final state evaporation residues were measured, thereby allowing a detailed study of the bombarding energy dependence of the production of specific isotopes. More accurate absolute cross sections for evaporation residue production were measured at several energies with a gas proportional $\Delta E$ solid state $E$ telescope. In this manner absolute cross sections were determined against which the $\gamma$-ray data could be normalized. The fusion cross section is found to vary smoothly with bombarding energy. Further, absolute cross sections agree well with model predictions currently in vogue.

NUCLEAR REACTIONS Fusion, measured ${\sigma }_{\mathrm{fusion}}\mathrm{}\left(E\right)\mathrm{}$; ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, $18.4\le E_{\mathrm{c}.\mathrm{m}.\mathrm{}}\le 35$ MeV. Compared with entrance channel and level density limitation models.

• Received 25 September 1981

DOI:https://doi.org/10.1103/PhysRevC.25.872