Floquet spectroscopy of hydrogenic states: Classical and quantal descriptions

Abstract

The responses of hydrogenic states of highly excited Rydberg atoms to dc and rf electric fields have been studied and the data interpreted from both classical and quantal viewpoints. The solution of the Schr\"odinger equation for this system leads to a network of progenitor and sideband states, a Floquet-Stark map that, although complex, exhibits regularities. These regularities are interpreted from a classical viewpoint by considering the near-Keplerian orbit of the valence electron as the dynamical entity rather than the electron itself. It is shown that the regularities in the Floquet-Stark map are the result of a commensurability of the dc Stark frequency and that of the applied rf. The experimental technique employed, Floquet spectroscopy, also provides data from which atomic parameters may be extracted, in this case the quantum of the (permanent) electric dipole moment (QDM) associated with hydrogenic manifolds of sodium Rydberg atoms. It is observed that the QDM's for sodium are larger than those for corresponding states of hydrogen. This observation is interpreted from a classical point of view.