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

The fusion excitation function of S-32 + Ca-48 has been experimentally studied in a wide energy range, from above the Coulomb barrier down to cross sections in the sub-mu b region. The measurements were done at INFN-Laboratori Nazionali di Legnaro, using the S-32 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 Akyuz-Winther barrier. Coupled-channels calculations using the M3Y + repulsion potential are presented for this system and for S-36 + Ca-48. 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 S-32 + Ca-48.