Compound states of high excitation in ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{21,22}{}_{}{}^{}\mathrm{Ne}$ have been observed, with good resolution, in the total neutron yield from the reactions ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}(\alpha , n){}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{17,18}{}_{}{}^{}\mathrm{O}(\alpha , n){}_{}{}^{20,21}{}_{}{}^{}\mathrm{Ne}$. Bombarding $\alpha$-particle energies were approximately from 1 to 5 MeV. Analysis of the area under the excitation curves gives $\alpha$-particle strength functions of $S_{\alpha }=0.029\mathrm{}\pm 0.030$ for ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$+$\alpha$, 0.030±0.023 for ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$+$\alpha$, and 0.022±0.010 for ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$+$\alpha$. For astrophysical purposes these strength functions are used to extrapolate the average cross sections to lower energies.

• Received 20 November 1972

DOI:https://doi.org/10.1103/PhysRevC.7.1356