A ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$ identifier of high detection efficiency was utilized to investigate the ($\alpha ,{}_{}{}^8{}_{}{}^{}\mathrm{Be}$) reaction on ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$, ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$, and ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ targets at bombarding energies between 65 and 72.5 MeV. Differential cross sections were measured from ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=20\mathrm{}°-70\mathrm{}°$ for solid targets and over a more restricted range for the nitrogen gas targets. Excitation functions were obtained over a larger energy range for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ targets. At these energies, the ($\alpha ,{}_{}{}^8{}_{}{}^{}\mathrm{Be}$) reaction was found to proceed predominantly via a direct $\alpha$-cluster pickup mechanism and to populate strongly only those levels consistent with this mechanism. The data were analyzed in the framework of the exact finite-range distorted-wave Born approximation. Absolute and relative $\alpha$-particle spectroscopic factors were extracted for 22 states. Good agreement was found between these experimental values and the theoretical predictions of Kurath and of Rotter for the extent of α clustering in these light nuclei.

NUCLEAR REACTIONS ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$, ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(\alpha ,{}_{}{}^8{}_{}{}^{}\mathrm{Be})$ $E_{\alpha }=65-72.5\mathrm{}$ MeV; measured $\sigma (E_f,\theta )$; energy levels ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^5{}_{}{}^{}\mathrm{He}$; resolution 450 keV; DWBA analysis, deduced $S_{\alpha }$ for 22 states, comparisons with theoretical $S_{\alpha }$.

• Received 27 April 1976

DOI:https://doi.org/10.1103/PhysRevC.14.815