Convenient location of a near-threshold proton-emitting resonance in ¹¹B

Nuclear clustering is arguably one of the most mysterious nuclear phenomena. Numerous examples of cluster-like weakly-bound and unbound states in light nuclei can be found in the proximity of particle decay thresholds.

These include the ground state of the Borromean halo nucleus ¹¹Li and the famous Hoyle resonance in ¹²C that is indispensable for the synthesis of heavier elements in stars.

Theoretically, it was argued that the appearance of such states is a generic phenomenon in any open quantum system, in which bound and unbound states strongly mix which results in an ‘aligned eigenstate’ of the system carrying many characteristics of a nearby decay channel.

In the recent paper, published in Phys. Rev. Lett., theorists from INP Cracow, GANIL, and FRIB tackled the recently-reported ß-delayed proton emission of the neutron halo ground state of ¹¹Be.

The puzzling decay has been explained by the existence of a resonance with total angular momentum and parity J^π=1/2⁺ in ¹¹B, carrying many characteristics of a nearby proton-decay channel.

Figure: The ß -delayed proton emission of ¹¹Be. The neutron halo ground state of ¹¹Be undergoes beta decay to an excited state of ¹⁰B, which lies just above the proton-decay threshold. This state subsequently decays to ¹⁰Be by emitting a proton.

GANIL contact person: M. Ploszajczak