Coupled-channel and semiclassical analysis of 4,6,8He + 197Au fusion near the Coulomb barrier

Fusion of 4,6,8He + 197Au has been investigated near and below the Coulomb barrier. Three complementary approaches were employed: (i) a quantum coupled-channels (CC) framework (with continuum discretized coupled-channels when breakup was relevant), (ii) a semiclassical treatment of the relative motion, and (iii) the Wong single-parabolic-barrier formula. The fusion cross-section σfus, barrier distribution Dfus = d2(Eσfus)/dE2, and fusion probability σfus were computed. Couplings to collective excitations and transfer/breakup channels were incorporated through the coupling matrix, while barrier transmission was evaluated via WKB penetrabilities. These couplings were shown to broaden the effective barrier distribution and to enhance sub-barrier tunneling relative to a one-barrier picture. Across all systems, the quantum CC description was found to reproduce the data most accurately, the semiclassical model was observed to capture the main systematics, and the Wong formula was used chiefly above the barrier as a baseline. In this way, the joint roles of nuclear structure and reaction dynamics in shaping fusion observables were delineated for light-on-heavy systems.