Dynamic effect of collision phase lockout in a gas of cold “dark” atoms

In a gas of slow atoms exhibiting the effect of coherent population trapping (CPT) on the sublevels of the ground state in a spatially nonuniform light field, rare collisions destroying the CPT state initiate the irreversible exchange of momentum between radiation and atoms. This exchange is manifested as an additional force that acts on the particles and is of geometric origin; i.e., it is determined only by the structure of the field of local CPT states. When this force is not masked by the standard collision change in atomic momentum, the observation of the kinetics of the particles may provide information on the physics of the collisions.