Optical Transition and Momentum Transfer in Atomic Wave Packets
  It is shown that the population Rabi-floppings in a lossless two-level atom, interacting with a monochromatic electromagnetic field, in general are convergent in time. The well-known continuous floppings take place because the restricted choosing of initial conditions, that is when the atom initially is chosen on ground or excited level before the interaction, simultaneously having a definite value of momentum there. The convergence of Rabi-floppings in atomic wave-packet-states is a direct consequence of Doppler effect on optical transition rates (Rabi-frequencies): it gradually leads to ''irregular'' chaotic-type distributions of momentum in ground and excited energy levels, smearing the amplitudes of Rabi-floppings. Conjointly with Rabi-floppings, the coherent accumulation of momentum on each internal energy level monotonically diminishes too. 
A. Zh. Muradyan (1 and 2), V. A. Poghosyan (1) ((1) Department of   Physics, Yerevan State University, 1 Alex Manukian, Yere...