Halo neutrons and the β decay of Li 11

The β decay of Li 11 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 Be 10 γ spectrum, both the half-lives of states in Be 10 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 B 11 e with uncertainties comparable to those obtained from neutron spectroscopy experiments. These data suggest that the β decay to the 8.81MeV state in Be 11 occurs in the Li9 core and that one neutron comprising the halo of Li 11 survives in a halolike configuration after the β-delayed neutron emission from this level.