A new measurement of the intruder configuration in 12 Be

Abstract A new 11 Be( d , p ) 12 Be transfer reaction experiment was carried out in inverse kinematics at 26.9 A 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 + 0.03 and 0.41 − 0.11 + 0.11 were extracted for the 0 1 + and 0 2 + states, respectively, in 12 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 12 Be were deduced, allowing a direct comparison with the theoretical predictions. It is evidenced that the ground-state configuration of 12 Be is dominated by the d -wave intruder, exhibiting a dramatic evolution of the intruding mechanism from 11 Be to 12 Be, with a persistence of the N = 8 magic number broken.