The elastic scattering of ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$+${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ has been measured at laboratory energies of 121.0 and 201.6 MeV. These data have been combined with existing lower energy ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$+${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ data in order to carry out a global optical model analysis. Calculations employing Woods-Saxon potentials yield good fits to the data without requiring explicitly energy-dependent parameters. In contrast, using a proximity form for the real potential requires an explicitly energy-dependent Woods-Saxon imaginary potential in order to achieve comparable quality fits. Notch perturbation calculations have been utilized to locate the radial region of the potential to which the scattering is sensitive. At all energies the imaginary potential is stronger than the real potential at the radius of maximum sensitivity. This dominance of the absorptive potential greatly limits the amount of information which can be gained about the real potential. Comparison of the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$+${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ system with other light heavy ion systems such as ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$+${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$+${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ suggests that the weak binding of ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ may be responsible for the strong absorption in this case.

NUCLEAR REACTIONS ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$(${}_{}{}^9{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$), $E_L=121.0\mathrm{} \mathrm{and} 201.6$ MeV, measured $\frac{d\sigma }{d\Omega }$; optical model analysis; deduced Woods-Saxon and proximity model optical parameters, $\frac{V}{W}$ ratios, fusion barriers. Comparison with ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$+${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ behavior.

• Received 11 January 1980

DOI:https://doi.org/10.1103/PhysRevC.21.2398