The interaction of 11Li with 208Pb

TL;DR

This study measured the fusion excitation function of 11Li with 208Pb, revealing that most interactions result in breakup, with a small fraction leading to complete fusion, providing experimental data to compare with theoretical predictions.

Contribution

First experimental measurement of the 11Li + 208Pb fusion excitation function across a range of energies, clarifying the fusion and breakup processes involved.

Findings

Most interactions result in breakup of 11Li.

Less than 11% of interactions lead to complete fusion.

Evaporation residues indicate breakup and quasi-breakup processes.

Abstract

Background: 11Li is one of the most studied halo nuclei. The fusion of 11Li with 208Pb 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 11Li + 208Pb reaction. Methods: A stacked foil/degrader assembly of 208Pb targets was irradiated with a 11Li beam producing center of target beam energies from above barrier to near barrier energies (40 to 29 MeV). The intensity of the 11Li beam (chopped) was 1250 p/s and the beam on-target time was 34 hours. The alpha-decay of the stopped evaporation residues was detected in a alpha-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 215At evaporation residues were associated with the fusion of 11Li with 208Pb. The 213,214At evaporation residues were formed by the breakup of 11Li into 9Li + 2n, with the 9Li fusing with 208Pb. The 214At evaporation residue appears to result from a "quasi-breakup" process. Conclusions: Most of 11Li + 208Pb interactions lead to breakup with a small fraction (<= 11%) leading to complete fusion.