Laser acceleration of atoms by nonlinear mechanism

A nonlinear threshold phenomenon at the interaction of the atoms with the two counter propagating light beams of the different frequencies is presented. The existence of a critical intensity of the interference field is shown, which is the threshold of nonlinear resonance, achieving in the field. This phenomenon leads to the atom acceleration or deceleration, depended on its initial velocity. Such acceleration/deceleration of the shock character, because of the impact with the potential barrier, occurs on ultrashort distances in the order of laser wavelengths and depends neither on the field magnitude nor on the interaction length.