A comprehensive study has been completed on the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ radiative-capture reactions ${}_{}{}^9{}_{}{}^{}\mathrm{Be}-({}_{}{}^3{}_{}{}^{}\mathrm{He},\gamma ){}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, leading to the first four states of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}({}_{}{}^3{}_{}{}^{}\mathrm{He},\gamma ){}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, leading to the first five states in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. Excitation functions have been extended to excitations of 45 and 35 MeV, respectively, by bombarding natural ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ and isotopically enriched ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ targets with ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ from the Wright Nuclear Structure Laboratory MP tandem accelerator. Angular distributions have been taken at many key energies. These experiments utilized a large NaI(Tl) $\gamma$-radiation detector and plastic-scintillator cosmic-ray anticoincidence shield built as part of this program, and the IBM 360/44 on-line data acquisition system. Several resonances have been found. The experiment appears to confirm the role of 3p-3h configurations immediately above the giant resonances of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. Microscopic $R$-matrix calculations based on the Wang and Shakin 1p-1h and 3p-3h ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ wave functions have been conducted. Detailed comparison of these calculations with our data and ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}(p,{\gamma }_0){}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ data suggests that the source of much of the intermediate structure seen in the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ giant resonance may stem from the mixing of 1p-1h doorway configurations with 3p-3h configurations.

[NUCLEAR REACTIONS ${}_{}{}^6{}_{}{}^{}\mathrm{Be}({}_{}{}^3{}_{}{}^{}\mathrm{He},\gamma )$, $E=3-26\mathrm{}$ MeV; ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}({}_{}{}^3{}_{}{}^{}\mathrm{He},\gamma )$, $E=3-16\mathrm{}$ MeV; measured $\sigma (E;E_{\gamma },\theta )$. ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ deduced levels $J$, $\pi$, resonance parameters. Natural ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ target. Enriched ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ target.]

• Received 8 September 1972

DOI:https://doi.org/10.1103/PhysRevC.9.76