Clarification of large-strength transitions in the beta decay of Be-11

The shape and normalization of the beta-delayed a spectrum from Be-11 was measured by implanting Be-11 ions in a segmented Si detector. The spectrum is found to be dominated by a well-known transition to the 3/2(+) state at E-x = 9.87 MeV in B-11. A significant increase in the observed decay strength towards the higher end of the Qp window means, however, that the 9.87 MeV state cannot alone be responsible for the transition. Using the R-matrix framework we find that the inclusion of an extra 3/2(+) state at E-x = 11.49(10) MeV is required to obtain a satisfactory description of the spectrum. Both states show large widths towards alpha decay, exhausting significant fractions of the Wigner limit, a typical signature of alpha clusterization. The observed Gamow-Teller strength indicates large overlaps between the two states and the ground state of Be-11.