Abstract

The two-proton radioactivity is a unique tool to study the nuclear structure beyond the proton drip-line. Since its discovery in 2002, the known emitters have been Mg-19, Fe-45, Ni-48, Zn-54 and Kr-67. Kr-67 was observed for the first time at the RIKEN Nishina Center in 2015. Its decay energy was measured at 1690(17) keV with a branching ratio of 37(14) %. The halflife, 7.4(30) ms, was found in contradiction with theoretical calculations, pointing out effects of decay dynamics and nuclear deformation.