M ay 2 01 8 A New Measurement of the Intruder Configuration in 12 Be

A new Be(d, p)Be transfer reaction experiment was carried out in inverse kinematics at 26.9A MeV, with special efforts devoted to the determination of the deuteron target thickness and of the required optical potentials from the present elastic scattering data. In addition a direct measurement of the cross section for the 0+2 state was realized by applying an isomer-tagging technique. The s-wave spectroscopic factors of 0.20 −0.04 and 0.41 +0.11 −0.11 were extracted for the 0+1 and 0 + 2 states, respectively, in Be. Using the ratio of these spectroscopic factors, together with the previously reported results for the p-wave components, the single-particle component intensities in the bound 0 states of Be were deduced, allowing a direct comparison with the theoretical predictions. It is evidenced that the ground-state configuration of Be is dominated by the d-wave intruder, exhibiting a dramatic evolution of the intruding mechanism from Be to Be, with a persistence of the N = 8 magic number broken.