title: Spectral properties of atoms in fields: A semiclassical analysis
abstract: We develop a semiclassical theory for the spectral rigidity of nonhydrogenic Rydberg atoms in electric fields, and evaluate the significant deviations from the well-known Poissonian behavior in the hydrogenic case. The resulting formula is shown to be in excellent agreement with the exact quantal result. We also investigate diamagnetic atoms; we find that, in contrast to the classically integrable atoms, diffraction has a small effect on the spectral rigidity in the classically chaotic atom. We show that our predictions can also be of use in the mixed phase space regime.
authors.affiliation: Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom.
authors.initials: PN
authors.lastname: Walker
authors.initials: TS
authors.lastname: Monteiro