EIT and diffusion of atomic coherence
  We study experimentally the effect of diffusion of Rb atoms on Electromagnetically Induced Transparency (EIT) in a buffer gas vapor cell. In particular, we find that diffusion of atomic coherence in-and-out of the laser beam plays a crucial role in determining the EIT resonance lineshape and the stored light lifetime. 
I. Novikova, Y. Xiao, D.F. Phillips and R.L. Walsworth