Elastic and inelastic excitation functions for the systems ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$+ ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+ ${}_{}{}^{28,29,30}{}_{}{}^{}\mathrm{Si}$ have been measured at ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=180\mathrm{}°$ from the Coulomb barrier up to $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=45\mathrm{}$ MeV (${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$+${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$), $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=52\mathrm{}$ MeV (${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$), and $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=32\mathrm{}$ MeV (${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+${}_{}{}^{29,30}{}_{}{}^{}\mathrm{Si}$). Over the whole energy range they all exhibit pronounced and regular broad oscillations ($0.5\lesssim \theta \lesssim 1.5$ MeV). Elastic and inelastic angular distributions up to ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=180\mathrm{}°$ were taken at five of the maxima and near a minimum of the excitation function for the system ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$. All angular distributions are oscillatory and exhibit a strong backward rise. The data are discussed in terms of a coherent superposition of a background and a resonant amplitude and in terms of the interference between the internal and barrier wave reflected by a deep optical potential.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$+${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$, measured elastic and inelastic $\sigma (\theta ,E)$, $14 \mathrm{MeV}<E_{\mathrm{c}.\mathrm{m}.\mathrm{}}<52\mathrm{} \mathrm{MeV}$, $15°<{\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}<180\mathrm{}°$, resonance and optical potential analysis.

• Received 29 September 1980

DOI:https://doi.org/10.1103/PhysRevC.24.1010