Super-strong β-decay of 11Li into 11Be ∗ (18 MeV) state: a probe for halo p-wave component?

Abstract

An experimental study of β-delayed charged particles (H, He, Be), neutrons and γ-rays that follow the 11Li β-decay, clearly indicates a β-feeding to an exited state at 18.1 MeV in 11Be with a large Gamow-Teller strength, B GT ≥ 1.0. The large strength of this β-transition implies a broad overlap of the 11Be ∗ state at 18.1 MeV and the ground state of 11Li. The deduced width of this resonance is ≅ 1 MeV. A strong suppression of the branch from 18.1 MeV state into the 10Be+n channel is observed. This branch, with the largest decay energy, has a partial width less than 1% of the total width. A centrifugal barrier consideration fails to explain this effect. A possible consequence of the observed effect for the 11Li structure is that the admixture of (p 1 2 ) 2 configuration in 11Li might be small.