Ionization of Rydberg atoms by circularly and elliptically polarized microwave fields

Analysis of orbital decay time for the classical hydrogen atom interacting with circularly polarized electromagnetic radiation

Here we show that a wide range of states of phases and amplitudes exist for a circularly polarized (CP) plane wave to act on a classical hydrogen model to achieve infinite times of stability (i.e., no orbital decay due to radiation reaction effects). An analytic solution is first deduced to show this effect for circular orbits in the nonrelativistic approximation. We then use this analytic result to help provide insight into detailed simulation investigations of deviations from these idealistic conditions. By changing the phase of the CP wave, the time t(d) when orbital decay sets in can be made to vary enormously. The patterns of this behavior are examined here and analyzed in physical terms for the underlying but rather unintuitive reasons for these nonlinear effects. We speculate that most of these effects can be generalized to analogous elliptical orbital conditions with a specific infinite set of CP waves present. The paper ends by briefly considering multiple CP plane waves acting on the classical hydrogen atom in an initial circular orbital state, resulting in "jump-like" and "diffusion-like" orbital motions for this highly nonlinear system. These simple examples reveal the possibility of very rich and complex patterns that occur when a wide spectrum of radiation acts on this classical hydrogen system.

Chaos and reconnection in relativistic cyclotron motion in an elliptically polarized electric field

A theoretical study of the relativistic cyclotron motion occurring in a uniform magnetic field and an oscillating electric field of arbitrary polarization is performed, which aims at determining the effect of the ellipticity and the strength of the electric field upon the integrability or nonintegrability of the system. Unless a circularly polarized electric field is used, the cyclotron system is nonintegrable and displays stochastic behavior in the region where resonance islands overlap. It is found, however, that the stochastic layers become increasingly thin as the polarization angle is moved closer toward pi/2 (circular polarization). If the polarization angle is held fixed and the electric field amplitude is increased, the Kolmogorov-Arnold-Moser curves separating the resonance islands experience a reconnection process through which the islands are topologically rearranged. When the rearrangement is accomplished, the phase space is occupied mostly by regular trajectories.