The Spectroscopy of Highly Excited Atoms

Abstract

Rydberg atoms—atoms in highly excited states—have become the focus of attention of a number of research groups, though approaches to the field have been along a variety of routes. Some studies, for example the precision measurements of fine structure in helium described by Wing and MacActam elsewhere in this volume, grew naturally out of systematic studies of low-lying states. Much of the work, however, approaches highly excited atoms as a more-or-less separate species with its own characteristic phenomena. Ionization by a static electric field, for instance, plays little if any role in conventional spectroscopy but can be of central importance to the study of highly excited atoms. Because field ionization encompasses both discrete state and continuum behavior, photoabsorption in a strong field can simultaneously display characteristics of bound-state resonant absorption, photoionization, and photoabsorption. As another example, the phenomenology of thermal collisions between molecules and Rydberg atoms can be dominated by inelastic processes between quasidegenerate levels, or by electron attachment, processes which are entirely absent in ground-state collisions.

A portion of this material was presented at the Fifth International Conference on Atomic Physics, Berkeley, 1976 and appears in the paper, “Highly Excited Atoms, ” by D. Kleppner in Atomic Physics, Vol. 5, Proceedings of the Fifth International Conference on Atomic Physics, Eds. R. Marrus, H. A. Shugart, and M. H. Prior, Plenum Press, New York (1977).