Two-proton radioactivity search

Abstract

Two-proton radioactivity, a spontaneous breakup of elements with emission of two protons, was predicted to exist near the proton drip line by V.I. Goldansky long time ago. The recent theoretical and experimental progress in a search for such an exotic nuclear decay is reviewed. In theory, the new three-body model which treats two-proton radioactivity as a genuine three-particle nuclear decay is considered. In experiment, the first evidence for two-proton decay of 45Fe is described. Four atoms of 45Fe, produced at the fragment separator of GSI, decayed via particle emission with a total energy of 1.1(1) MeV and a half-life of 3.2 −1.0 +2.6 ms. A possible experiment for a direct observation of two-proton emission from the ground state of 19Mg is considered for its decay in-flight. The half-life of 19Mg, as well as proton-proton correlations, might be derived from the distribution of the 19Mg decay vertices extrapolated from the measured trajectories of all fragments.