BUNCHING AND ANTIBUNCHING OF DE-EXCITED ATOMS LEAVING A MICROMASER

The joint probability of detecting two successive atoms both in the lower state at the exit of a micromaser is calculated. We find that this joint probability, in dependence on the atomic flux N(ex), takes values greater (bunching) or smaller (antibunching) than that for uncorrelated events. The regions of N(ex) where antibunching (bunching) occurs, correlate fairly well with the regions where sub(super)-poissonian statistics for the number fluctuations of atoms leaving the maser in the lower state has been predicted and recently observed. This coincidence is shown to result from the fact that both the bunching/antibunching phenomenon and the number fluctuations are governed by the photon statistics of the maser field in a similar way.