C12(O16,α)Mg24Excitation Functions and Statistical-Model Calculations for High-Spin States inMg24

High-resolution excitation functions were measured in the energy range $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=19\mathrm{}-25$ MeV for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^{16}{}_{}{}^{}\mathrm{O},\alpha )$ reaction to highly excited states in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ ($E_{\mathrm{exc}}\approx 13.5-17.5$ MeV). The strong, rapid observed fluctuations suggest a predominately compound-nucleus reaction mechanism. The selective population of high-spin states in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ by the present reaction in contrast to the lack of such selectivity in the ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}({}_{}{}^{14}{}_{}{}^{}\mathrm{N},\alpha )$ reaction can readily be explained by Hauser-Feshbach statistical-model calculations. A fluctuation analysis indicates coherence widths of 90-150 keV, and cross correlations were found to be small and thus compatible with a purely statistical compound-nucleus process.