Cross sections at up to 15 angles and in 10 keV steps between $13.4<\mathrm{}{E}_{\alpha }<20.8\mathrm{}$ MeV for both ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$($\alpha$,${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$($\alpha$,${\alpha }_i$)${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ are reported. The absolute cross sections indicate (via detailed balance) serious systematic errors in published ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$,$\alpha$)${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ cross sections. The data show much resonant structure and, using the ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$($\alpha$,${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ data, $J^{\pi }$ assignments and extracted resonant parameters for 55 states in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ can be found, only 10 of which had been assigned previously. The systematics of these states seem more consistent with the Friedman-Goebel barrier top resonances than with "quasimolecular" resonances. The alpha scattering data show little correlation with the ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$($\alpha$,${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ channel.

NUCLEAR REACTIONS ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$($\alpha$,${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$; measured $\sigma (E,\theta )$ at up to 15 angles. ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$($\alpha$,${\alpha }_0{\alpha }_1{\alpha }_2{\alpha }_3{\alpha }_4{\alpha }_5{\alpha }_6{\alpha }_{10}{\alpha }_{11}{\alpha }_{13}$) measured $\sigma (E,\theta )$ at one or two angles. $13.4<\mathrm{}{E}_{\alpha } \left(\mathrm{MeV}\right)<\mathrm{}20.8\mathrm{}$, $\Delta E_{\alpha }=10\mathrm{}$ keV. Deduced ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ level parameters $J^{\pi }$, $\Gamma$, $\frac{{\left({\Gamma }_{\alpha }{\Gamma }_c\right)}^{\frac{1}{2}}}{\Gamma }$, $E_r$. Ne gas target.

• Received 23 March 1981

DOI:https://doi.org/10.1103/PhysRevC.24.1891