Tests of the Exponential Decay Law at Short and Long Times

Abstract

We have studied the $\beta$ decays of ${}_{}{}^{60}{}_{}{}^{}\mathrm{Co}$ at times $\lesssim {10}^{-4\mathrm{}}{t}_{\frac{1}{2}}$ and those of ${}_{}{}^{56}{}_{}{}^{}\mathrm{Mn}$ over the interval $0.3t_{\frac{1}{2}}\le t\le 45t_{\frac{1}{2}}$ to search for proposed deviations from the exponential decay law at short and long times, respectively. Over all time periods examined, our data are consistent with purely exponential behavior. From these measurements, stringent limits are derived on the amplitudes of possible deviations from the exponential decay law.