Seven elastic scattering angular distributions have been measured for the system ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ around the first resonant structure observed in the ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=180\mathrm{}°$ excitation function at 21.1 MeV center of mass energy just above the Coulomb barrier. Optical model, Regge pole, and phase shift analyses have been performed. These complementary analyses show that several partial waves contribute to the backward rise and the oscillatory behavior of the elastic scattering angular distributions. The 21.1 MeV resonant structure can be interpreted in terms of several overlapping resonances. Tentative spin assignments are made for these states.

[NUCLEAR REACTIONS Elastic scattering of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$(${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$). Seven angular distributions measured between 18.67 and 22.29 MeV, angular range 25° to 176° c.m. Optical model, Regge pole, and phase shift analyses.]

• Received 27 June 1983

DOI:https://doi.org/10.1103/PhysRevC.29.147