The ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(\mathrm{p}, \alpha ){}_{}{}^9{}_{}{}^{}\mathrm{B}$ and ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}(\mathrm{p}, \alpha ){}_{}{}^{29}{}_{}{}^{}\mathrm{P}$ reactions have been studied at incident energies of 42.77 and 41.9 MeV, respectively. The experimental (p, $\alpha$) relative cross sections are well reproduced by distorted wave direct pickup calculations with a semimicroscopic form factor and current shell model wave functions. A comparison between (p, $\alpha$) and (${}_{}{}^3{}_{}{}^{}\mathrm{He}$,d) spectra on $1p$ and $2s-1d$ shell nuclei, leading to the same final nucleus, shows a clear evidence of a dominant pickup process over the knockout mechanism in the dynamics of the (p, $\alpha$) reaction.

NUCLEAR REACTIONS, NUCLEAR STRUCTURE ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(\mathrm{p}, \alpha ){}_{}{}^9{}_{}{}^{}\mathrm{B}$, $E=42.77\mathrm{}$ MeV, ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}(\mathrm{p}, \alpha ){}_{}{}^{29}{}_{}{}^{}\mathrm{P}$, $E=41.9\mathrm{}$ MeV, measured $\sigma (E_x, \theta )$; natural targets. DWBA analysis. Calculated ${}_{}{}^9{}_{}{}^{}\mathrm{B}$ energy levels, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(\mathrm{p}, \alpha ){}_{}{}^9{}_{}{}^{}\mathrm{B}$ and ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}(\mathrm{p}, \alpha ){}_{}{}^{29}{}_{}{}^{}\mathrm{P}$ spectroscopic strengths.

• Received 1 March 1983

DOI:https://doi.org/10.1103/PhysRevC.28.42