Time-resolved saturated-absorption experiment. Effect of velocity-changing collisions upon non-thermal-equilibrium atomic velocities

Results obtained in a time-resolved study of atomic-velocities thermalization for the ¹D₂ metastable level of the barium transition 6 ¹P₁ → 5 ¹D₂ are presented. Time evolution of the absorption coefficient after saturation due to a strong monochromatic laser pulse is studied. The results are analyzed in the strong-collision model, including trapping effects in the ¹P₁ level. For barium and rare-gas mixtures the cross sections for strong elastic collisions are in agreement with the cross sections deduced from the kinetic theory.