Halo nucleus Be-11: A spectroscopic study via neutron transfer

TL;DR

This study uses neutron transfer reactions to precisely measure the spectroscopic factors of Be-11's halo neutrons, providing new insights into its nuclear structure and confirming the weakly bound nature of its halo.

Contribution

It offers the first consistent and optical-potential-insensitive measurements of Be-11's spectroscopic factors using inverse kinematics and the adiabatic model.

Findings

Spectroscopic factor for 2s1/2 state: 0.71(5)

Spectroscopic factor for 1p1/2 state: 0.62(4)

Results are consistent across four beam energies

Abstract

The best examples of halo nuclei, exotic systems with a diffuse nuclear cloud surrounding a tightly-bound core, are found in the light, neutron-rich region, where the halo neutrons experience only weak binding and a weak, or no, potential barrier. Modern direct reaction measurement techniques provide powerful probes of the structure of exotic nuclei. Despite more than four decades of these studies on the benchmark one-neutron halo nucleus Be-11, the spectroscopic factors for the two bound states remain poorly constrained. In the present work, the Be-10(d,p) reaction has been used in inverse kinematics at four beam energies to study the structure of Be-11. The spectroscopic factors extracted using the adiabatic model, were found to be consistent across the four measurements, and were largely insensitive to the optical potential used. The extracted spectroscopic factor for a neutron in a nlj = 2s1/2 state coupled to the ground state of Be-10 is 0.71(5). For the first excited state at 0.32 MeV, a spectroscopic factor of 0.62(4) is found for the halo neutron in a 1p1/2 state.