Dynamics of alkali Rydberg atoms in time-varying external fields

The theory of Rydberg atoms in time-varying external fields is significantly simplified if the O(4) dynamical symmetry property of the non-relativistic Coulomb problem can be exploited. The O(4) symmetry is, however, broken by core interactions in Rydberg atoms other than hydrogen. In this paper, we consider lithium atoms as a special example and show that core effects are so pronounced in the dynamics that a hydrogen-like treatment is invalid. This conclusion holds in general for alkali atoms. The inclusion of core interactions represents a substantial improvement in comparison with available experimental data, although significant departures still remain to be explained.