Chaotic ionization of a Rydberg atom subjected to alternating kicks: Role of phase-space turnstiles

Abstract

We study the ionization of a highly excited Rydberg atom subjected to a periodic sequence of external electric-field pulses. Such systems are important laboratory and theoretical models of classical and quantum chaos. Furthermore, a good theoretical understanding of this chaos is important for controlling electronic states in atoms, as has been demonstrated in a series of recent experiments on the creation and control of electronic wave packets. Here, we present a theoretical analysis of the chaotic ionization of a hydrogen atom subjected to alternating positive and negative impulses. This analysis is based on the observation that the ionization of the atom is due to a turnstile in phase space which promotes the electronic state from negative to positive energy. The geometry of the lobes associated with the turnstile provides a clear picture of how the ionization process proceeds. Using this geometric intuition, we propose two experimental protocols to directly reveal the importance of the turnstile lobes in the laboratory.