The neutron-unbound nucleus Be-15 was observed for the first time. It was populated using neutron transfer from a deuterated polyethylene target with a 59 MeV/u Be-14 beam. Neutrons were measured in coincidence with outgoing Be-14 particles and the reconstructed decay energy spectrum exhibits a resonance at 1.8(1) MeV. This corresponds to Be-15 being unbound by 0.45 MeV more then Be-16 thus significantly hindering the sequential two-neutron decay of Be-16 to Be-14 through this state.
Snyder, J., T. Baumann, G. Christian, R. A. Haring-Kaye, Paul A. DeYoung, Z. Kohley, B. Luther, M. Mosby, A. Simon, J. K. Smith, A. Spyrou, S. Stephenson and M. Thoennessen. "First Observation of Be-15." Physical Review C 88, no. 3 (2013).