Kicked Rydberg atom: Response to trains of unidirectional and bidirectional impulses

Abstract

The behavior of $\mathrm{Rb}(390p)$ atoms subject to a train of up to 50 half-cycle pulses (HCPs) with duration ${T}_{p}\ensuremath{\ll}{T}_{n},$ where ${T}_{n}$ is the classical electron orbital period, is investigated. In this limit, each HCP simply delivers an impulsive momentum transfer or ``kick'' to the electron. The response of atoms to a series of unidirectional kicks and to a series of kicks that alternate in direction is compared. For unidirectional kicks, the Rydberg atom survival probability has a pronounced maximum when the pulse repetition frequency ${v}_{p}$ is \ensuremath{\sim}1.3 times the classical orbital frequency ${v}_{n}.$ Classical simulations show this behavior provides a signature of dynamical stabilization. Evidence of dynamical stabilization and chaotic diffusion is also found in the distribution of final bound states. Very different behavior is observed for alternating kicks. The survival probability generally increases with ${v}_{p},$ although a small local maximum is evident when ${v}_{p}\ensuremath{\sim}{v}_{n}.$ Little evidence of dynamical stabilization is observed in either the calculated dependence of the survival probability on the number of applied kicks, in the measured final bound-state distribution, or in the classical phase space of the kicked atom. Model calculations for a one-dimensional ``atom'' reveal islands of stability, but their three-dimensional counterparts are found to be unstable.