Spectroscopy of 13Be through isobaric analog states in 13B

Background: Spectroscopy of the exotic, neutron unbound beryllium isotope 13Be is still a puzzle despite significant experimental efforts.Purpose: We aim to observe T = 5/2 states in 13B, establish spin-parities and spectroscopic factors, and use isospin symmetry to inform spectroscopy of 13Be. Methods: Excitation functions for resonance elastic scattering of 12Be on protons were measured in the center -of-mass energy range from 1 to 5 MeV.Results: Two T = 5/2 states in 13B 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 12Be +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 13Be as 5/2+ and infer the existence of an s-wave (1/2+) resonance at around 0.6 MeV with relatively small spectroscopic factor.