Spectroscopy of beryllium-12 using the (lithium-7, beryllium-7) reaction in inverse kinematics

The quenching of the N = 8 shell gap has been under investigation for more than 40 years, yet there remains significant controversy over the extent of mixing between 0ho and 2ho configurations in 12Be. Recent neutron knockout and transfer measurements have helped quantify 2ho contributions to the ground and excited 0+ states. The current study measures the 0ho component of the 0+ wavefunctions for the first time.;The Gamow-Teller strength (B(GT)) of transitions from the ground state of 12B to the 0+ states in 12Be has been measured using the (7Li, 7Be) charge-exchange reaction in inverse kinematics. Since the ground state of 12B is dominated by 0ho configurations, Gamow-Teller (DeltaL=0, DeltaS=1 ) transitions to 0+ states in 12Be selectively probe the 0ho component of the wavefunction.;The extracted B(GT) to the 0+ states in 12Be were compared with shell model calculations, performed using the code OXBASH and employing a modified WBP interaction in the spsdpf model space. To reproduce the observed B(GT) distribution, a 0hDelta admixture of 25.48+/-5.49% is required in the ground state of 12Be, and a 0hDelta admixture of 59.83+/-4.78% is required in the the 2.24 MeV 0+ state. These results are compared with the wavefunctions extracted from neutron knockout and transfer measurements, and the theoretical predictions of Fortune and Sherr, Barker, and Romero-Redondo et al.