Abstract
Excited states in the nucleus , with one neutron outside the double magic core, were populated following one-neutron knockout from a beam on a carbon target at relativistic energies at the Radioactive Isotope Beam Factory at RIKEN. Besides the rays emitted in the decay of the known neutron single-particle states in additional strength in the energy range 3.5–5.5 MeV was observed for the first time. Since the neutron-separation energy of is low, , this observation provides direct evidence for the radiative decay of neutron-unbound states in this nucleus. The ability of electromagnetic decay to compete successfully with neutron emission at energies as high as 3 MeV above threshold is attributed to a mismatch between the wave functions of the initial and final states in the latter case. These findings suggest that in the region southeast of nuclear structure effects may play a significant role in the neutron versus competition in the decay of unbound states. As a consequence, the common neglect of such effects in the evaluation of the neutron-emission probabilities in calculations of global -decay properties for astrophysical simulations may have to be reconsidered.
- Received 28 February 2017
DOI:https://doi.org/10.1103/PhysRevLett.118.202502
© 2017 American Physical Society