Fusion enhancement in the 38S+208Pb reaction

The capture-fission cross section was measured for the reaction of S-38 with Pb-208 for center-of-mass projectile energies E-cm of 160-265 MeV. The S-38 beam was prepared by projectile fragmentation at the NSCL at higher energies and degraded to 4-7 MeV/nucleon. The time of flight (energy) of each interacting beam particle was measured along with the fission fragments. The data were compared to previous measurements of the capture-fission excitation function for the S-32+Pb-208 reaction. The interaction barrier for the S-38-induced reaction is 16.1 +/- 10.1 MeV lower than the S-32-induced reaction whereas the reduced excitation functions for the two reactions are similar. A discussion of the systematics of barrier shifts in the fusion of n-rich nuclei is given and the implications of this shift for the synthesis of heavy nuclei with radioactive beams are discussed.