Response of highly polarized Rydberg states to trains of half-cycle pulses -: art. no. 033402

The response of very-high-n strongly polarized potassium Rydberg atoms to a sequence of impulsive perturbations provided by a train of short unidirectional electric pulses is investigated. Each pulse, termed a half-cycle pulse (HCP), has a duration T-p<T-n, where T-n is the classical electron orbital period. Pronounced differences in the survival probability are observed when the sequence of HCPs is directed parallel and antiparallel to the axis of polarization of the initial state. For impulses directed antiparallel to the initial state, Poincare surfaces of section point to a mixed phase space with large stable islands embedded in a chaotic sea that can lead to dynamical stabilization. Stable islands are absent when the direction of the impulses is reversed. The system is globally chaotic leading to rapid ionization. We show that noise, i.e., random fluctuations in the temporal pulse-to-pulse spacing as well as in the pulse amplitude, plays a crucial role in the degree of dynamical stabilization. Reasonable agreement between experiment and theory is achieved.