The Periodically Driven excited Hydrogen Atom

This article describes the e ects of relatively strong, periodic perturbations on the classical and quantum dynamics of excited hydrogen atoms and the relation between these two dynamics. By considering a range of driving frequencies it is shown how the relative ratio of this to the unperturbed atomic frequencies a ects the response and the relation between the classical and quantum dynamics. After providing an introduction to the system a brief overview of its behaviour in six di erent frequency regimes is given. This is followed by a detailed discussion of the response of a one-dimensional atom driven by a resonant eld describing the subtle relations between the classical and quantum dynamics. This discussion is followed by a description of the more complex response of a three-dimensional hydrogen atom to a low frequency elliptically polarised eld where, again, we demonstrate that the relative time scales of the system a ect the dynamics in unexpected ways.