Phase-dependent energy transfer in a microwave field

Abstract

We have excited Li atoms to Rydberg states with a picosecond laser in the presence of a phase-locked microwave field. We have observed energy transfer to higher- and lower-lying Rydberg states depending on the phase of the microwave field at which the picosecond laser excitation occurs. These observations confirm the prediction of a classical picture of the energy transfer and demonstrate that the phase-dependent energy transfer is not limited to processes in which energy transfer occurs across the ionization limit.