Evidence from angular distributions and excitation functions of the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, $\alpha$) ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ suggests the identification of the 7.20-MeV $0^{+}$ and 7.83-MeV $2^{+}$ states in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ with the [220] quartet configuration—i.e., two $\mathrm{sd}$-shell $\alpha$ particles outside a ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ core. It appears that these states are populated via a "semidirect" mechanism that proceeds through the formation of doorway states in the incident channel.

• Received 16 July 1971

DOI:https://doi.org/10.1103/PhysRevLett.27.950