The ac Stark effect was used to induce resonant energy transfer between translationally cold Rydberg atoms. The Rb Rydberg atoms were obtained by laser excitation of cold atoms from a magneto-optical trap. Using two-photon microwave spectroscopy of the 49s_{ 1/2}-50s_{ 1/2} transition, the field strength of a 28.5 GHz dressing field was calibrated. When this dressing field was set at specific field strengths, the two-atom dipole-dipole process 43d_{ 5/2} + 43d_{ 5/2} -> 45p_{ 3/2} + 41f was dramatically enhanced, due to induced degeneracy of the initial and final states. A series of observed resonant field strengths correspond to different magnetic sublevel possibilities for the initial and final states. These agree well with calculated resonance fields based on a perturbative ac Stark shift formula. This method for enhancing interactions is complementary to dc electric-field-induced resonant energy transfer, but has more flexibility due to the possibility of varying the applied frequency.
Categories: physics.atom-ph