Influence of Ground State Hyperfine Pumping on Light-Induced Drift Velocity of Atoms

In the light-induced drift phenomenon, ground state hyperfine pumping has an obvious effect on the population at each energy level of an atom and further on the light-induced drift velocity. The research on the influencing mechanism of ground state hyperfine pumping is helpful to optimize the drift velocity and the selectivity of isotope separation. We build the atomic light-induced drift rate equations and utilize the strong collision model to describe the collision between atoms and buffer gases. The rate equations are solved numerically, and the influence of ground state hyperfine pumping on light-induced drift is investigated. The research results show that ground state hyperfine pumping has an obvious suppression effect on light-induced drift. The larger the ground state hyperfine splitting energy difference is, the stronger the suppression effect on light-induced drift is. Increasing laser power density and laser linewidth and simultaneously using the second laser to re-pump atoms populating at the other ground state hyperfine energy level to the excited state energy level can weaken the effect of ground state hyperfine pumping and enhance the light-induced drift velocity. The research results are basically consistent with the qualitative analysis based on the physical principles and also the experimental results from some related literatures.