Two neutron decay of ¹⁶Be

¹ Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824, USA
² Lawrence Livermore National Laboratory, L-414, Livermore, California 94551, USA

^a e-mail: lovell@nscl.msu.edu
^b e-mail: nunes@nscl.msu.edu
^c e-mail: IJT@ianthompson.org

Published online: 25 March 2016

Abstract

Recently, the first example of two-neutron decay from the ground state of an unbound nucleus, ¹⁶Be, was seen (A. Spyrou, et. al., Phys. Rev. Lett. 108 102501 (2012)). Three-body methods are ideal for exactly treating the degrees of freedom important for these decays. Using a basis expansion over hyperspherical harmonics and the hyperspherical R-matrix method, we construct a realistic model of ¹⁶Be in order to investigate its decay mode and the role of the two-neutron interaction. The neutron-¹⁴Be interaction is constrained using shell model predictions. We obtain a ground state for ¹⁶Be that is under-bound by approximately 0.7 MeV with a width of approximately 0.17 MeV. For such a system, an attractive three-body force must be included to reproduce the experimental ground state energy.