CROSS-SECTION MEASUREMENTS FOR ELECTRON-IMPACT ON EXCITED ATOMIC SPECIES

This chapter reviews differential and integral (DCS and Q, respectively) cross-section measurement techniques and available cross-section data for electron collisions with excited neutral atoms. The chapter discusses methods for the production and detection of excited atoms, with emphasis on recent methods that relate to cross-section measurements. A number of improved electron-impact excitation and charge-exchange schemes have been reported in recent years for the production of metastable atoms and with the availability of lasers, it is now also possible to produce large populations in levels with short radiative lifetimes, as well as in metastable levels through cascade processes. The latter method is, however, not yet fully exploited. Quantitative cross-section measurements require the knowledge of excited atom densities (at least relative to ground state species) and, in cases where more than one excited species are present, the relative densities of these species. The methods for determining these densities are described. © 1993 Academic Press Inc.