Entrance Channel Phenomena in Complex Nuclear Scattering

The elastic scattering excitation functions of the systems ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$-${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$-${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$-${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$-${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$-${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$-${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$-${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$, and ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$-${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ have been subjected to comparative optical-model analyses. The gross structure characteristic of all these excitation functions is shown to arise from potential scattering phenomena. These phenomena have been studied in detail. The extracted ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$-${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ potential has been used as input to detailed studies leading to the identification of single partial-wave orbiting resonances of 3- to 4-MeV width. The ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$-${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ experimental data have also been used to test for the possible existence of a variable-moment-of-inertia effect during the interpenetrating collisions; no evidence for such an effect has been found, at least in this particular case. New suggestions for the prediction of the imaginary optical-potential parameters have been investigated.