Investigating halo features in ¹⁰Be with the ¹¹Be(p,d)¹⁰Be* transfer reaction at 110 MeV at TRIUMF-ISAC II

Abstract

One-neutron transfer reactions are used to study single-particle neutron states in nuclei. In this work, the 11Be(p,d)10Be* transfer reaction at 9.93 MeV/nucleon was performed at the TRIUMF-ISAC II facility with the Printed Circuit Board Based Charged Particle ((PCB)2) array inside the TRIUMF ISAC Gamma- Ray Escape-Suppressed Spectrometer (TIGRESS). Using particle identification and particle-γ coincidence the extraction of angular distributions was performed for the ground state and all the populated excited states of 10Be (2+1 , 2+2 , 1− and 2−). A collective state model was used in an attempt to fit the angular distributions for the 0+1 and 2+1 states by deforming a 10Be potential with a quadrupole coupling in DWBA calculations run by FRESCO. This model correctly predicted the magnitude of the angular distribution for the 0+1 state, but did not successfully reproduce the angular distribution for the 2+1 state. The other 10Be states were modeled as a single-particle hole states using either a one- or two-step process to create the hole state by removing a p3/2 neutron from the initial configuration of the 11Be nucleus. To extract the spectroscopic factors for the hole states, a χ2 analysis was performed to find the best fit to the experimental data. After the spectroscopic factors were extracted they were compared to theoretical predictions and previous experimental values. The spectroscopic factors of the 1− and 2− single-particle hole states starting from a pure s1/2 state were found to be lower than previous studies, however, it was also determined in this analysis that a d5/2 component of the wavefunction could be significant in some cases. The spectroscopic factor of the single-particle hole state for the 2+2 state was found to be extremely large to reproduce the magnitude of the cross-section. Further studies are needed to resolve the structure of the 2+2 state. The 2− state remains the best candidate for an excited halo state structure, though the s1/2 spectroscopic factor is much lower than predicted. An experiment to extend the angular distributions beyond what was measured in this experiment could provide more sensitivity to the s1/2 and d5/2 components and perhaps clarify the s1/2 and d5/2 makeup of the 1− and 2− states.