Particularities of optical pumping effects in cold and ultra-slow beams of Na and Cs in the case of cyclic transitions

摘要

The time-dependent population dynamics of hyperfine (HF) levels of n (2) p (3/2) states is examined for cyclic transitions in alkali atoms. We study a slow and cold atomic beam of Na (n = 3) and Cs (n = 6), taking into account the long interaction time of light with atoms (200 mu s) inside the resonant laser beam. Simple analytical expressions for the populations of the excited states and for the intensities of the absorption lines are derived for a three-level system model. We show that at moderate pump laser power the mixing of HF levels is sufficient to form a flow of population from a cyclic transition to partially open transitions. We discuss various phenomena associated with the evolution of optical pumping that cannot be explained by general analysis of two-level system model.