Spontaneous decay of an atom excited in a dense and disordered atomic   ensemble: quantum microscopic approach
  On the basis of general theoretical results developed previously in [I. M. Sokolov et al., J. Exp. Theor. Phys. 112, 246 (2011)], we analyze spontaneous decay of a single atom inside cold atomic clouds under conditions when the averaged interatomic separation is less or comparable with the wavelength of quasi resonant radiation. Beyond the decay dynamics we analyze shifts of resonance as well as distortion of the spectral shape of the atomic transition. 
A.S. Kuraptsev and I.M. Sokolov
physics.atom-ph quant-ph