The Spectroscopy of Atomic Compound States

Abstract

This brief report on the spectroscopy of compound states of atoms presents a discussion of their energy levels, widths, spectral classification, and modes of decay. Generally, mention is not made of intensities or oscillator strengths as reliable estimates are frequently not available because of the difficulties of absolute calibration of apparatus. Reference to theoretical treatments of the subject is made only to clarify the nature of the levels. Diagrams and tables of energy levels are given. The comprehensive review by Schultz(1) in 1973 considered atomic compound states primarily as short-lived, excited states of negative ions which arose either from the temporary capture of electrons in collision with neutral atoms or from the excitation of fast negative ions in various collision processes with gaseous targets. The interesting feature of these negative ion states is that they overlap an adjacent continuum of states of the neutral atom with a consequent interaction of configurations which strongly influences their nature. A more general concept of a compound state includes all states whose nature is determined by configuration interaction effects rather than by an independent particle description and so, in the widest sense, includes nearly all atomic states. The following section discusses some general features of atomic states and then narrows the contents of the paper to atomic states that lie in a continuum.