Excitation functions of the total proton and $\alpha$-particle yields from the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ reaction have been measured in the range $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=12.9\mathrm{} \mathrm{to} 27.4$ MeV, with angular distribution measurements at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=14.9,21, \mathrm{and} 26.6$ MeV. For comparison, the elemental distribution of evaporation residues was also measured at the latter three energies. The $\alpha$ excitation curve exhibits structure corresponding to the oscillations seen in an earlier measurement of the total fusion cross section, while the proton cross section increases rather smoothly with energy. At 15 MeV all the proton and $\alpha$ cross section is accounted for by the observed evaporation residues, but an increasing excess of light-ion production is seen at the higher energies. The excess cross section, if interpreted as $3\alpha$ production, compensates for the previously observed decrease in fusion cross section below the expected total reaction cross section.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^{16}{}_{}{}^{}\mathrm{O},p)$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^{16}{}_{}{}^{}\mathrm{O},\alpha )$, $E_{\mathrm{lab}}=30\mathrm{}-64$ MeV, measured $\sigma (\theta ,E)$; ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^{16}{}_{}{}^{}\mathrm{O},x)$, $E_{\mathrm{lab}}=35, 49, 62$ MeV, measured $\sigma (\theta ,Z)$.

• Received 18 February 1977

DOI:https://doi.org/10.1103/PhysRevC.16.673