Decay mechanism and lifetime of Kr-67

Abstract

The lifetime of the recently discovered 2p emitter Kr-67 was found to be considerably below the lower limit predicted theoretically. This communication addresses this issue. Different separation energy systematics are analyzed and different mechanisms for 2p emission are evaluated. We find that the most plausible reason for this disagreement is the decay mechanism of 67Kr, which is not "true 2p" emission but rather "transitional dynamics" on the borderline between true 2p and sequential 2p decay mechanisms. If this is correct, this imposes stringent limits of E-r = 1.35-1.42 MeV on the ground-state energy of Br-66 relative to the Se-65-p threshold