Experimental study of the nature of the 1− and 2− excited state

Abstract

The nature of the 1− and 2− excited states in 10Be is studied using the 11Be(p, d) transfer reaction in inverse kinematics at 10A MeV at TRIUMF ISAC-II, in particular to assess whether either of them can be considered as an excited halo state. The angular distributions for both states are extracted using deuteron-γ coincidences and analyzed using a transfer model taking into account one-step and two-step processes. A good fit of the angular distributions is obtained considering only the one-step process, whereby an inner p3/2 neutron of 11Be is removed, leaving the halo neutron intact. Higher-order processes however cannot be rejected. The small spectroscopic factors extracted suggest that the structure of both states is not uniquely halo-like, but rather display a more complex configuration mixing cluster and halo structures. Further insights are limited, as this experiment specifically probed the halo-like (but not cluster-like) 11Be(1/2+) ⊗ (ν p3/2 ) −1 configuration in both states.