Structures in high-energy fusion data

Structures observed in heavy-ion fusion cross sections at energies above the Coulomb barrier are interpreted as caused by the penetration of centrifugal barriers that are well-separated in energy. The structures are most pronounced in the fusion of lighter, symmetric systems, where the separation in energy between successive angular momentum barriers is relatively large. It is shown that the structures or peaks can be revealed by plotting the first derivative of the energy weighted cross section. It is also shown how an orbital angular momentum can be assign to the observed peaks by comparing to coupled-channels calculations. This is illustrated by analyzing high-energy fusion data for $^{12}$C+$^{16}$O and $^{16}$O+$^{16}$O, and the possibility of observing similar structures in the fusion of heavier systems is discussed.