The Production and Detection of Spatially Localized Atomic Electron Wave Packets

Abstract

One of the least understood areas of modern physics is the border between the realms of microscopic and macroscopic physics. In principle, both realms are governed by quantum theory, but typically it is difficult to describe the macroscopic world in terms of quantum theory, although it can be accurately described by classical theory. In the microscopic realm, the predictions of quantum theory are highly accurate while classical theory has serious difficulties. What happens at the border between the two realms? Recently this border has been explored by several experiments. The experiments fall into two categories. Both categories study an highly excited atomic system. The first group of experiments explore the response of the highly excited atom to an ionizing field. A classical description of this atom- field system exhibits chaotic motion. For example, the microwave ionization of hydrogen has been the focus of many of these experiments.^1,2 For a certain set of parameters, the ionization threshold agrees with the onset of chaotic motion in the classical model. By establishing the parameters for which the chaotic ionization occurs, the classical limit of this system is more clearly defined. The second group of experiments study highly excited coherent states of the atom. These states have spatially localized wave packets that have both strong classical and quantal characteristics. The goal of these experiments^3-6 is to produce states that are spatially localized and evolve like classical atoms. The ability of the experiments to produce such states also gives a measure of the classical limit of the atomic system. The research in this paper falls into the second category describing the observation of Rydberg atom wave packets in the vapor of alkali metal atoms.