Resonance enhancement of two photon absorption by magnetically trapped atoms in strong rf-fields

TL;DR

This paper predicts a significant enhancement in two-photon transition probabilities in magnetically trapped cold rubidium atoms due to avoided crossings in Floquet energy levels caused by strong polychromatic rf-fields, with potential applications in rf-spectroscopy.

Contribution

The study introduces a many-mode Floquet formalism to explain resonance enhancement in two-photon transitions in cold atoms under strong rf-fields, revealing new physical phenomena.

Findings

Large two-photon transition probability predicted

Avoided crossings cause resonance enhancement

Transition probabilities vary periodically with rf mode separation

Abstract

Applying a many mode Floquet formalism for magnetically trapped atoms interacting with a polychromatic rf-field, we predict a large two photon transition probability in the atomic system of cold $^{87}Rb$ atoms. The physical origin of this enormous increase in the two photon transition probability is due to the formation of avoided crossings between eigen-energy levels originating from different Floquet sub-manifolds and redistribution of population in the resonant intermediate levels to give rise to the resonance enhancement effect. Other exquisite features of the studied atom-field composite system include the splitting of the generated avoided crossings at the strong field strength limit and a periodic variation of the single and two photon transition probabilities with the mode separation frequency of the polychromatic rf-field. This work can find applications to characterize properties of cold atom clouds in the magnetic traps using rf-spectroscopy techniques.