Measurements and analysis of response function of cold atoms in optical molasses

We report our experimental measurements and theoretical analysis of the position response function of cold atoms in a magneto-optical trap (MOT) by applying a transient homogeneous magnetic field as a perturbing force. We observe a transition from a damped oscillatory motion to an over-damped relaxation, stemming from a competition between the viscous drag provided by the optical molasses and the restoring force of the MOT. Our observations are in agreement with the predictions of our model based on the Langevin equation. We also study the diffusion of the atomic cloud in the optical molasses and find the measured value of diffusion coefficient matching with the prediction of our theoretical model.