4D-imaging of drip-line radioactivity by detecting proton emission from 54mNi pictured with ACTAR TPC

Proton radioactivity was discovered exactly 50 years ago. First, this nuclear decay mode sets the limit of existence on the nuclear landscape on the neutron-deficient side. Second, it comprises fundamental aspects of both quantum tunnelling as well as the coupling of (quasi)bound quantum states with the continuum in mesoscopic systems such as the atomic nucleus. Theoretical approaches can start either from bound-state nuclear shell-model theory or from resonance scattering. Thus, proton-radioactivity guides merging these types of theoretical approaches, which is of broader relevance for any few-body quantum system. Here, we report experimental measurements of proton-emission branches from an isomeric state in Ni-54m, which were visualized in four dimensions in a newly developed detector. We show that these decays, which carry an unusually high angular momentum, l = 5 and l = 7, respectively, can be approximated theoretically with a potential model for the proton barrier penetration and a shell-model calculation for the overlap of the initial and final wave functions. Proton radioactivity is useful for studying nuclear structure. Here the authors report two proton emission branches from the 10+ state isomer of 54mNi by using a time projection chamber.

Automated summary

Proton radioactivity, discovered 50 years ago, is important for studying nuclear structure and has various theoretical approaches. Experimental measurements of proton emission branches from the isomeric state in Ni-54m show high angular momentum decays that can be theoretically approximated. In this study, two proton emission branches from the 10+ state isomer of 54mNi were reported using a new detector.