Resonant Backward-Angle Heavy-Ion Elastic Scattering

Abstract

We observe strong structure in the excitation functions of $^{12}\mathrm{C}$ + $^{28}\mathrm{Si}$ backward-angle scattering. Angular distributions at the peaks of the elastic excitation function are of the form ${{P}_{J}}^{2}(cos\ensuremath{\theta})$ [approximately $J=15$ (${E}_{\mathrm{c}.\mathrm{m}.}=23.3$ MeV), $J=18$ (${E}_{\mathrm{c}.\mathrm{m}.}=26.0$ MeV), and $J=18$ (${E}_{\mathrm{c}.\mathrm{m}.}=30.2$ MeV)]. These results appear to be inconsistent with existing theoretical descriptions of anomalous backward-angle heavy-ion elastic scattering in this mass region.