Selective alpha particle decay ofC12+C12resonances to excitedNe20rotational bands observed in theC12(C12,α)Ne20reaction

Excitation functions of the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^{12}{}_{}{}^{}\mathrm{C},\alpha ){}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ reaction were measured at ${\theta }_{\mathrm{lab}}=7.5\mathrm{}°$ between $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=14-40\mathrm{}$ MeV and angular distributions were measured from $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=17.8\mathrm{} \mathrm{to} 20.6$ MeV. Summed yields reveal prominent intermediate structure resonances over the entire range which correlate well to resonances previously observed in elastic data. The resonances show enhanced decays to excited rotational bands in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ with reduced widths comparable to those for the elastic channel and an order of magnitude greater than those for the ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ ground state band. A discussion is given of the resonances as shape-isomeric states in a shell model secondary minimum in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, and of the selective alpha decay as being transitions to states of related configuration in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$.