The interaction of 11Li with 208Pb

Abstract

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