Fusion Cross Section Measurements for the Silicon -28 + CARBON-12, SULFUR-32 + CARBON-12 and CALCIUM-40 + CARBON-12 Systems.

Fusion cross section measurements have been made for the ('28)Si + ('12)C, ('32)S + ('12)C and ('40)Ca + ('12)C systems using gamma ray techniques. Excitation functions for the production of twelve residual nuclides in the ('28)Si + ('12)C reaction have been obtained over the energy range of 18.0 - 42.0 MeV c.m. Large, regular structures, comparable to those previously observed only in lighter systems involving ('12)C and ('16)O ions, were observed in the energy region of the Coulomb barrier. A significant fraction of the oscillatory behavior comes from the nucleon decay exit channels. This unusual behavior of the fusion data is accompanied by strongly correlated, back angle elastic and inelastic scattering data which appears uncorrelated to the fusion data. Excitation functions for the production of ten residual nuclides in the ('32)S + ('12)C reaction have been measured over the energy range of 16.3 - 29.4 MeV c.m. Structure in the total fusion yield was observed which is significantly weaker and less regular than that in the ('28)Si + ('12)C system. The most strongly structured exit channels in the ('32)S + ('12)C system, and also in the ('28)Si + ('12)C system, are the 2p and (alpha)p evaporation residues. One fusion structure in the ('32)S + ('12)C system, identified at 28.2 MeV, occurs at the same energy as structures in both back angle elastic and inelastic scattering data for the same system. Excitation functions for the production of six residual nuclides in the ('40)Ca + ('12)C reaction have been measured over the energy range of 19.6 - 22.8 MeV c.m. The total fusion yield increases smoothly with energy.