Fine structure in the elastic and inelastic scattering ofC12+Si28andO16+Si28

The ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=180\mathrm{}°$ elastic and inelastic excitation functions have been measured for the systems ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ ($27.8\le E_{\mathrm{c}.\mathrm{m}.\mathrm{}}\le 31.5$ MeV) and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ ($30.0\le E_{\mathrm{c}.\mathrm{m}.\mathrm{}}\le 32.7$ MeV) in small steps ($\delta E_{\mathrm{c}.\mathrm{m}.\mathrm{}}<100\mathrm{}$ keV). In both systems it is observed that the gross structures previously found ($\Gamma \approx 1-2$ MeV) are strongly split into finer structure. A statistical analysis of the data has been made to determine the average width, strength, and cross correlation of these narrow structures. The results are compared to the predictions of Hauser-Feshbach calculations. It is concluded that it is impossible within the standard statistical model to simultaneously reproduce both the observed widths and the average fluctuating cross sections.