Rydberg States: Properties and Applications to Electrical Discharge Measurements

Abstract

If an electron in an atom is excited to a level designated by a high principal quantum number n where n is typically greater than 10, the level is termed a Rydberg level (Stebbings and Dunning, 1983) and the atom is often called a Rydberg atom (Bayfield, 1983; Kleppner et al., 1983). These states have been observed from a wide variety of plasma sources in the laboratory and also from astrophysical sources. In interstellar space the Rydberg levels are formed by radiative recombination. Emission from Rydberg states of atomic hydrogen have been distinguished from the continuum radiation with n as high as 732. In laboratory plasmas, dissociative recombination, cumulative excitation and optical excitation are more likely excitation processes. The development of powerful tunable dye lasers into the ultraviolet permits the selective excitation of many atoms and molecules to high Rydberg states. Recently (Rinneberg et al., 1985) Rydberg states of barium with principal quantum numbers up to 290 have been observed under laboratory conditions. Figure 1 illustrates the photoexcitation method of the helium metastable states that we have used to investigate glow discharge conditions.