BOOSTED GLOW-DISCHARGES FOR ATOMIC SPECTROSCOPY - ANALYTICAL AND FUNDAMENTAL PROPERTIES

Low pressure glow discharge sources with plane or hollow cathodes are frequently used in spectrochemical analysis, either as sources for opt ical emission spectroscopy or as primary sources for atomic absorption spectrometry. Increasingly they are also used as ion sources for mass spectrometry. The analytical performances may frequently be improved by ''boosting'' the intensity of the source by using an auxiliary disc harge (dc radio frequency or microwave), by using a magnetic field or by modifying the structure of the source. This review concentrates on sources for optical spectroscopy, discusses the various types of boost ed source, the extent to which they have been adopted and the improvem ent obtained in analytical performance. The amount of work published o n the fundamental properties of these sources is limited. Lines of ana lytical interest increase greatly in intensity; other modifications to the spectra are very complex, but a study of the literature shows tha t similar changes in the electrical and spectral properties of the sou rce are observed in widely different forms of boosted discharge. These changes are described and some are interpreted in terms of fundamenta l excitation processes, but much further work will be required before a full understanding of boosted discharges is obtained.