Reaction mechanism populating 12 C + 16 O breakup states in 28 Si

A measurement of the ${}^{12}\mathrm{C}{+}^{16}\mathrm{O}$ breakup of ${}^{28}\mathrm{Si}$ following ${}^{24}\mathrm{Mg}$ scattering from targets of carbon, lithium oxide, and beryllium has been performed. A study of the relative energy of the correlated ${}^{12}\mathrm{C}$ and ${}^{16}\mathrm{O}$ fragments has allowed the excitation energy of states in ${}^{28}\mathrm{Si}$ to be determined. A comparison of the excitation energy spectra in ${}^{28}\mathrm{Si}$ obtained from the three targets indicates that the same states are populated in the ${}^{12}\mathrm{C}{(}^{24}\mathrm{Mg}{,}^{12}{\mathrm{C}}^{16}\mathrm{O}{)}^{8}\mathrm{Be},$ ${}^{7}\mathrm{Li}{(}^{24}\mathrm{Mg}{,}^{12}{\mathrm{C}}^{16}\mathrm{O})t,$ and ${}^{9}\mathrm{Be}{(}^{24}\mathrm{Mg}{,}^{12}{\mathrm{C}}^{16}\mathrm{O}{)}^{5}\mathrm{He}$ reactions. The data support the hypothesis that the reaction mechanism populating the ${}^{12}\mathrm{C}{+}^{16}\mathrm{O}$ breakup states observed in these channels is $\ensuremath{\alpha}$ transfer, and rule out an alternative involving resonant, or ``doorway,'' states in the ${}^{12}\mathrm{C}{+}^{24}\mathrm{Mg}$ compound system.