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Institute of Optics

bar_yell

Angularly Localized Wave Packets in One- and Two-Electron Atoms

by

James A. West
(1997)


We examine angularly-localized wave packets in atoms with one and two valence electrons.

In hydrogenic systems we use elliptic states to formulate a classical interpretation for core scattering. Classical and quantum results are compared for hydrogen and sodium in the presence of a dc electric field. The correspondence is excellent in hydrogen but in sodium the Stark dynamics of the elliptic state can be divided into two components revealing scattered and unscattered behavior. An experimental investigation of this result is proposed in which a new elliptic state excitation scheme is evaluated for use in sodium.

Fundamental to all Rydberg wave packet studies are efficient excitation schemes for transferring population to highly excited states. Using dressed state and density matrix modeling of a two-pulse stepwise transfer in a sodium ladder system, we find that transfer of population is most e.cient when the pulses are applied in a counterintuitive order. An experimental investigation in a sodium vapor cell veri.es this result in the presence of Doppler broadening, Gaussian spatial averaging and fluctuations of the lasers. The experimental results also reveal that the counterintuitive excitation scheme is less sensitive to fluctuations than in the reverse pulse-ordering.

In studies of the classical limit of two-electron systems a new class of planetary states is described in which both electrons are excited, but the atom is stable against autoionization. We simplify the problem through an adiabatic approximation which allows a self-consistent separation of the dynamics of the two electrons. We find that to a good approximation, the effect of the outer, more energetic, electron on the inner electron can be modeled by an external electric field, while the effect of the inner electron on the outer one can be modeled as simple dynamical screening of the atomic core charge. The resulting orbits are a unique class of shape-preserving orbits in which no angular momentum is exchanged. A fully quantum mechanical description of a single-electron atom in an external field is shown to agree well with the two-electron classical simulation of the shape-preserving orbits.


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Last modified 13 September 2006