Structures in high-energy fusion data

TL;DR

This paper explains structures in high-energy fusion cross sections as resulting from centrifugal barrier penetration, revealing peaks through derivative plots and assigning angular momentum via coupled-channels calculations, with analysis of specific light-ion systems.

Contribution

It introduces a method to interpret fusion cross section structures as centrifugal barrier effects and demonstrates how to identify angular momentum of peaks using coupled-channels calculations.

Findings

Structures are caused by well-separated centrifugal barriers.

Peaks can be revealed by plotting the derivative of energy weighted cross sections.

Angular momentum can be assigned to peaks through coupled-channels analysis.

Abstract

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.