Halo neutrons and the β decay of11 Li

Abstract

The βdecay of 11Li has been investigated at TRIUMF-ISAC using a high-efficiency array of Compton suppressed HPGe detectors. From a line-shape analysis of the Doppler-broadened peaks observed in the 10Be γ spectrum, both the half-lives of states in 10Be and the energies of the β-delayed neutrons feeding those states were obtained. Furthermore, it was possible to determine the excitation energies of the parent states in 11Be with uncertainties comparable to those obtained from neutron spectroscopy experiments. These data suggest that the ́ decay to the 8.81 MeV state in 11Be occurs in the 9Li core and that one neutron comprising the halo of 11Li survives in a halolike configuration after the β-delayed neutron emission from this level.