A narrow near-threshold proton-emitting resonance ($E_x=11.4\mathrm{MeV}$, $J^{\pi }=1/2^{+}$, and ${\mathrm{\Gamma }}_p=4.4\mathrm{keV}$) was directly observed in ${}^{11}\mathrm{B}$ via proton resonance scattering. This resonance was previously inferred in the $\beta$-delayed proton emission of the neutron halo nucleus ${}^{11}\mathrm{Be}$. The good agreement between both experimental results serves as a ground to confirm the existence of such exotic decay and the particular behavior of weakly bound nuclei coupled to the continuum. $R$-matrix analysis shows a sizable partial decay width for both, proton and $\alpha$ (${\mathrm{\Gamma }}_{\alpha }=11\mathrm{keV}$) emission channels.

• Received 11 February 2022
• Revised 29 April 2022
• Accepted 1 June 2022

DOI:https://doi.org/10.1103/PhysRevLett.129.012501

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Published by the American Physical Society