Study of β-delayed charged particle emission of ¹¹Li: Evidence of new decay channels

The break-up of the 18.2 MeV state in ¹¹Be was studied in a ¹¹Li β-decay experiment. We report here on the study of the dominating breakup channels involving na⁶He or 3n2α in the final state, with special emphasis dedicated in this contribution to the three-particle channel. The two emitted charged particles were detected in coincidence using a highly segmented experimental set-up. The observed experimental energy-vs-energy scatter plot indicates a sequential breakup where nuclei of mass 4, alpha particles, and mass 7, ⁷He, are involved. A Monte-Carlo simulation of the sequential channel, ¹¹Be* → α + ⁷He → nα⁶He was performed and compared to the experimental data and to a simulation of the direct break-up of the 18.2 MeV state nα⁶He by phase space energy distribution. The energy-versus-energy plot are explained by the sequential simulation but not by the phase space simulation.