Two-proton Radioactivity: the Interesting Case of \(^{67}\)Kr and Further Studies

We report on the observation of Kr-67 that has been produced in an experiment performed at the RIKEN/BigRIPS facility. The two-proton decay of Kr-67 has been evidenced and this nucleus is thus the fourth observed long lived ground-state two-proton emitter, after Fe-45, Ni-48 and Zn-54. In addition, the decay of several isotopes in the mass region has been investigated. While for previous cases of two-proton radioactivity, the theoretical models could reproduce the measured data, this is not the case anymore for Kr-67. Two interpretations have been proposed to explain this discrepancy: a transition between real two-proton and sequential decay or the influence of deformation. These hypotheses will be tested in future experiments by measuring the angular and energy correlations of the emitted protons.