Exploring Non-Exponential Decay in Isomeric Transitions

Wade Scates
Idaho State University
Department of Physics

In quantum mechanics the survival probability of unstable systems are predicted to deviate from the classical exponential law when the time after production of the system – the "age" of the system" -- is very small (t << t½) or very large (t >> t½).  This effect is commonly referred to as non-exponential decay, or NED.  Though this effect is predicted to occur in all unstable systems, the nuclear system in which it is expected to be easiest to observe is long-lived isomeric transitions.  Through the experiments reported herein, bounds are placed on the time after production that non-exponential decay effects influence the survival probability of the isomeric state.   An upper bound between the early NED effects and exponential decay, or ts, was found to be ts <1.2x10-4 t½.  Furthermore, a lower bound between exponential decay and the late NED effects, tl, was measured to be tl >19.5 t½.