Modulation and correlation of the radial and angular motions of a Rydberg electron in a resonance microwave field

We discuss the physical sense and interpretation of the Maeda–Gallagher experiment (2004) in which the probability of ionisation of Rydberg Li atoms perturbed by the resonance microwave field by a short half-cycle pulse was measured. The periodic dependence of the ionisation probability w_i on the delay time t₀ of the half-cycle pulse with respect to the instant of switching on the microwave field is found. The oscillation period of the function w_i(t₀) is equal to the Kepler period of a Rydberg electron. It is shown that the interpretation of this experiment by the authors in terms of localised wave packets has no grounds and neglects basic processes proceeding in the microwave field. An alternative interpretation is proposed and, as the first step, the structure of the Rydberg wave function formed in the resonance microwave field is studied.