Characterization of a radio frequency glow discharge emission source

Abstract

A radio frequency glow discharge atomic emission source is described. This source incorporates two optical windows, one positioned such that both the glow region of the discharge and the sample surface may be viewed simultaneously, and the other positioned such that only the glow may be viewed. Preliminary signal-to-noise ratios obtained with the two optical geometries are compared and found to be similar. However, optical monitoring of both the glow and sample surface results in significantly higher emission intensities, owing to the more complete viewing of the energetic regions of the discharge. As a result, this geometry may be considered to be analytically more advantageous. Additionally, data are presented to illustrate the dependences of the dc self-bias potential, excitation temperature, sputter rate, and emission intensities of sputtered species on discharge pressure and generator output power. Scanning electron micrographs of the surface of a machinable glass ceramic (MACOR) sample indicate that appreciable sputtering of electrically nonconductive solid samples occurs in the rf glow discharge. Comparison of data acquired with conductive and nonconductive samples is made to show the similar behavior of the discharge in the presence of the two sample types. Exemplary spectra are presented to illustrate the potential usefulness of the source for the emission spectrometric analysis of both electrically conductive and nonconductive solids.