Spectroscopy of Be 13 through isobaric analog states in B 13

Abstract

Background: Spectroscopy of the exotic, neutron unbound beryllium isotope Be13 is still a puzzle despite significant experimental efforts. Purpose: We aim to observe T=5/2 states in B13, establish spin-parities and spectroscopic factors, and use isospin symmetry to inform spectroscopy of Be13. Methods: Excitation functions for resonance elastic scattering of Be12 on protons were measured in the center-of-mass energy range from 1 to 5 MeV. Results: Two T=5/2 states in B13 at excitation energies 18.25 and 19.95 MeV were observed. Unambiguous 1/2+ and 5/2+ spin-parity assignments were made, and spectroscopic factors were established using the R-matrix analysis of the measured Be12+p excitation functions. Conclusions: We provide the first direct and unambiguous spin-parity assignments and spectroscopic factor measurements for the resonances in the A=13, T=5/2 isobaric multiplet. This puts us on a solid footing to identify the 2.3 MeV state in Be13 as 5/2+ and infer the existence of an s-wave (1/2+) resonance at around 0.6 MeV with relatively small spectroscopic factor. © 2023 American Physical Society.