First Observation Of Two‐Proton Radioactivity Of 45Fe

In experiments at the FRS of GSI and at the SISSI‐LISE3 facility of GANIL, the decay of the proton drip‐line nucleus 45Fe has been studied after projectile fragmentation of a 58Ni primary beam. Fragment‐implantation events have been correlated with radioactive decay events in silicon telescopes on an event‐by‐event basis. The decay‐energy spectrum of 45Fe implants shows a distinct peak consistent with a two‐proton ground‐state decay of 45Fe. None of the events in the peak were found to be in coincidence with γ radiation or with β particles which were searched for in the telescope‐surrounding detectors. The decay energy for 45Fe agrees nicely with several theoretical predictions for two‐proton emission. These predictions strongly support the observed decay to be a simultaneous two‐proton ground‐state decay.