Nuclear structure effects on over-barrier fusion reactions investigated with a new phenomenological model

We investigate the occurrence of nuclear structure effects in the cross section of heavy-ion fusion reac-tions at energies above the Coulomb barrier. To this end, we initially develop a universal phenomenolog-ical model capable to reproduce, with an unprecedented accuracy, all previously published experimental fusion excitation functions with a few parameters. The new model, which foresees exclusively charge, mass, and energy of the colliding systems, shows a clear saturation of the critical angular momentum and avoids analytical non-regularities. The predictions of the newly developed model are then inspected to pin down residual discrepancies with the data, which could be ascribed to the structure of the col-liding systems. In this framework, we obtain the following findings: (1) for the first time, we suggest an anomaly in the optimum value of the fusion cross section for systems having nearly-zero fusion Q-values; (2) we point out the occurrence of shell closure effects in the fusion of light systems; (3) we suggest that shell effects are washed-out at relative velocities vrel >= 0.07c; (4) in the higher energy part of the fusion excitation function, the cross section for colliding systems involving fluorine or neon isotopes impinging on 2p3/2-1 f5/2 nuclei is suppressed, possibly due to the occurrence of alpha-clustering effects enhancing alpha-transfer reactions. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3.