Search for beta-delayed proton emission from 11 Be

8 pags., 4 figs., 4 tabs.We report on an attempt to reproduce the observation of β-delayed proton emission from Be through detection of the final state nucleus Be with accelerator mass spectrometry. Twelve samples were collected at the ISOLDE facility at CERN at different separator settings, allowing tests of different sources of contamination to be carried out. The observed amounts of Be per collected Be rule out several contamination sources, but do not agree internally. Formation of BeH molecular ions in the ion source may explain our data, in which case an upper limit of the βp branching ratio of 2.2 × 10 can be derived.We would like to acknowledge support from the European Union’s Horizon 2020 research and innovation programme under Grant agreement no. 654002, from the Spanish research projects FPA2015-64969- P, FPA2015-65035-P and FPA2017-87568-P (MINECO/FEDER, UE), and from the Danish Council for Independent Research (DFF-4181- 00218)