Resonances inO16+O16

Unambiguous $S$ matrix elements (resonant and background contributions) have been extracted from data on the reaction ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, (${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$,${\alpha }_0$)${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$. Assignments of $J^{\pi }={10}^{+}, 8^{+}, \mathrm{and} 8^{+}$ have been made to resonances at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=15.8, 15.9, \mathrm{and} 16.1$ MeV, respectively: Nonresonant amplitudes result from a narrow angular momentum window about the $l=10\mathrm{}$ grazing partial wave; at 90° these dominate the reaction. Systematic behavior of the $8^{+}$ resonances in this and other heavy-ion systems suggest that they may not be of binary character and that $\alpha$-particle substructure may play a role.