Effects of transfer channels on near- and sub-barrier fusion of ^{32}S + ^{48}Ca

The fusion excitation function of 32S + 48Ca has been experimentally studied in a wide energy range, from above the Coulomb barrier down to cross sections in the sub-μb region. The measurements were done at INFN–Laboratori Nazionali di Legnaro, using the 32S beam from the XTU Tandem accelerator. The excitation function has a smooth behavior below the barrier, and no evident hindrance character shows up in the measured energy region. The fusion barrier distribution has a peculiar shape with two distinct peaks of similar height, lower and higher than the Akyüz-Winther barrier. Coupled-channels calculations using the M3Y + repulsion potential are presented for this system and for 36S + 48Ca. The results of these calculations give a good account of the data, and indicate the influence of one- and two-nucleon transfer channels with positive Q values, which are only open for 32S + 48Ca.