Resonant dynamics of the H atom in an elliptically polarized microwave   field
  The dynamics of Rydberg states of atomic hydrogen driven by elliptically polarized microwaves of frequency fulfilling 2:1 classical resonance condition is investigated both semiclassically and quantum mechanically in a simplified two-dimensional model of an atom. Semiclassical results for quasienergies of the system are shown to be in a good agreement with exact quantum data. The structures of the quantum states are found to reflect the underlying classical dynamics; especially we show the existence of nonspreading wavepackets propagating on elliptical trajectories. 
Krzysztof Sacha and Jakub Zakrzewski