Quantum recoil effects in finite-time disentanglement of two   distinguishable atoms
  Starting from the requirement of distinguishability of two atoms by their positions, it is shown that photon recoil has a strong influence on finite-time disentanglement and in some cases prevents its appearance. At near-field inter atomic distances well localized atoms, with maximally one atom being initially excited, may suffer disentanglement at a single finite time or even at a series of equidistant finite times, depending on their mean inter atomic distance and their initial electronic preparation. 
F. Lastra, S. Wallentowitz, M. Orszag, and M. Hernandez