Collective and Independent-Particle Motion in Simple Atoms and Molecules: a Unification?

Abstract

The evidence is reviewed that implies electrons in doubly-excited states of helium behave like the atoms of a linear triatomic molecule. The relation between molecule-like collective motion and independent- particle, solar-system-like motion is explored via the model problem of two interacting particles on concentric spheres. The state of understanding of independent-particle motion for atoms in small polyatomic molecules is surveyed briefly and the proposal is explored that some small molecules, such as dihydrides, might exhibit independent-particle rotational motion in sufficiently highly excited local mode states.