Spatially Localized Rydberg Electronic Wave Packets

by

John A. Yeazell
(1990)

The problem of forming a spatially localized electronic wave packet, in a bound atomic system, is studied. The intent is to form a wave packet which has strong classical characteristics and behavior. Such a state would occupy the same role for the atomic system as the coherent state fills for the harmonic oscillator. These states offer a system where the relationship of classical and quantal mechanics can be studied.

Two experiments are described in which coherent superpositions of Rydberg atomic states are excited by a short, optical pulse. Each experiment studies a different type of superposition and the resulting wave packet. Both types of wave packets can be described, in part, by classical theory. The results of the experiments are compared with the predictions of the classical theory.

In the first experiment, a superposition of states, that have different principal quantum numbers, is formed. The resulting wave packet is localized in the radial dimension. The radial motion of this wave packet is periodic with the period of the classical Kepler orbit. This periodicity was observed in the photoionization signal produced by a delayed, short pulse. As the wave packet oscillated between the inner and outer turning points, the photoionization rate changed. The beats in the photoionization signal were found to be separated by the classical orbital period.

The second experiment used a technique for exciting high angular momentum Rydberg states to form a superposition of states with different angular momentum quantum numbers. The resulting wave packet is localized along an elliptical trajectory about the nucleus. The localization affected the ionization of the wave packet by a pulsed dc electric field. A classical model of the ionization process was developed that accurately predicted the experimental results.

Finally, the feasibility of exciting a wave packet, which combines the characteristics of both of the above wave packets, is studied numerically.

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Last modified 13 September 2006