The interaction of 11Li with 208Pb

Background: Li-11 is one of the most studied halo nuclei. The fusion of Li-11 with Pb-208 is the subject of a number of theoretical studies with widely differing predictions, ranging over four orders of magnitude, for the fusion excitation function. Purpose: The purpose was to measure the excitation function for the Li-11 + Pb-208 reaction. Methods: A stacked foil and degrader assembly of Pb-208 targets was irradiated with a Li-11 beam producing center-of-target beam energies from above-barrier to near-barrier energies (40-29 MeV). The intensity of the Li-11 beam (chopped) was 1250 particles/s and the beam on-target time was 34 h. The a decay of the stopped evaporation residues (EVRs) was detected in an a-detector array at each beam energy in the beam-off period (the beam was on for <= 5 ns and then off for 170 ns). Results: The observed nuclidic yields of At-212/215 and At-214 are consistent with being produced in the complete fusion of Li-11 with Pb-208. The observed yields of At-213 appear to be the result of the breakup of Li-11 into Li-9 + 2n, with the Li-9 fusing with Pb-208. The magnitudes of the total fusion cross sections are substantially less than most theoretical predictions. Conclusions: It is possible to measure the EVR production cross sections resulting from the interaction of Li-11 with Pb-208 using current-generation radioactive beam facilities. Both complete fusion and breakup fusion processes occur in the interaction of Li-11 with Pb-208. An important breakup process leads to the fusion of the Li-9 fragment with Pb-208. DOI: 10.1103/PhysRevC.87.044603