FLUCTUATIONS IN RADIOACTIVE DECAYS .1. NONEQUILIBRIUM EFFECTS AND NOISE

Radioactive decay is a nonequilibrium process. For most practical purp oses it can be modeled as a steady-state process, but there are instan ces where counting statistics should not be assumed constant; this rem ark is particularly relevant for long counting intervals. We give expl icit formulas for the probability distribution of counts, the expected values of the mean, the variance, and the Allan variance. These formu las, rather than the Poissonian ones, should be used as benchmark for experiments aimed at revealing exotic effects. Formulas are compared t o numerical simulations and actual experiments.