C12+C12elastic scattering excitation functions and phase shift analysis

The ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$+ ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ elastic scattering has been measured for $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=14.6-31.3\mathrm{}$ MeV, ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=30\mathrm{}°-110\mathrm{}°$. The elastic data have been analyzed via a phase shift analysis, enabling the extraction of model independent sets of phase shift parameters. The extracted $J^{\pi }$ values for the intermediate structure resonances at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=18.4, 19.3, \mathrm{and} 20.3$ MeV are ${12}^{+}$, ${12}^{+}$, and ${12}^{+}$ or ${14}^{+}$, respectively. The questions of ambiguities in the phase shift analysis and the comparison with $J^{\pi }$ values deduced from other experiments are discussed. Evidence is presented for the existence of gross structure resonances. The elastic scattering has also been analyzed using the sum-of-differences method to directly extract the total reaction cross section. The results of these analyses are compared to existing models of the origin of intermediate structure resonances.