The dominance of the v(0d(5/2))(2) configuration in the N=8 shell in Be-12 from the breakup reaction on a proton target at intermediate energy

摘要

The momentum distribution of Be-11 fragments produced by the breakup of Be-12 interacting with a proton target at 700.5 MeV/u energy has been measured at GSI Darmstadt. To obtain the structure information on the anomaly of the N = 8 neutron shell, the momentum distribution of Be-11 fragments from the one-neutron knockout Be-12(p, pn) reaction, measured in inverse kinematics, has been analysed in the distorted wave impulse approximation (DWIA) based on a quasi-free scattering scenario. The DWIA analysis shows a surprisingly strong contribution of the neutron 0d(5/2) orbital in Be-12 to the transverse momentum distribution of the Be-12 fragments. The single-neutron 0d(5/2) spectroscopic factor deduced from the present knock-out data is 1.39(10), which is significantly larger than that deduced recently from data of Be-12 breakup on a carbon target. This result provides a strong experimental evidence for the dominance of the neutron v(0d(5/2))(2) configuration in the ground state of Be-12. (c) 2017 The Authors. Published by Elsevier B.V.