Interpretation of Gross Structures in the Energy Spectra of the ReactionC12(O16,α)Mg24

Recent studies of the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$,$\alpha$)${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ at $E\left({}_{}{}^{16}{}_{}{}^{}\mathrm{O}\right)=145\mathrm{}$ MeV have revealed the existence of several broad states with $E_x\left({}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}\right)=20\mathrm{} \mathrm{to} 60$ MeV, which have been interpreted as members of the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ molecular band $J^{\pi }=\left({10}^{+}\right)$ through $J^{\pi }=\left({18}^{+}\right)$. Subsequent investigation, however, has failed to reveal the expected partial width for ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$*→${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$+${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. We show that these states can be interpreted as an extension of the ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ yrast sequence which is populated by the well understood high-spin selectivity of $\alpha$-particle evaporation from a ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ compound nucleus.