Chaotic ionization of highly excited hydrogen atoms

Abstract

Recent experimental measurements of the microwave ionization of highly excited hydrogen atoms with principal quantum numbers ranging from n = 30 to 90 are well described by a classical treatment of the nonlinear electron dynamics. In particular, the predictions of the threshold field for the onset of significant ionization is found to coincide with the onset of classical chaos in a one-dimesional model of the experiment. In this brief note I emphasize that this excellent agreement between the theoretical and experimental ionization thresholds requires a proper theoretical treatment of the slow, adiabatic turn-on of the microwave perturbation in which the persistence on nonlinear resonances in the chaotic phase space plays a crucial role.