Self-absorption in Quantitative Glow Discharge Emission Spectrometry

Abstract

The emission intensities of five resonance atomic lines affected by self-absorption were investigated as a function of analyte concentration in a sample for a Grimm-type atomization/excitation source operated in the dc mode in argon. Based on considerations of radiative transfer within the source, and using the two-layer model and other approximations, the equationwas derived, linking the emission intensityI_E^M, the sputter rateq^Mand the analyte concentrationc_E^Min the matrix, whereE is a particular element in a matrix M. The R_E0andβ_E constants resulting from fitting the experimental data to this relationship were investigated as functions of GD operating conditions. It was shown thatR_E0can be regarded as the (generalized) emission yield. Dependence of theR_E0andβ_E parameters on discharge operating conditions suggests that they could reflect more fundamental processes occurring in the discharge. Comparison ofβ_Efactors for different lines, however, leads to results that are not explicable within the adopted model. Methodology of quantitative GD-OES analysis was generalized to be applicable also to self-absorption lines with non-linear intensity responses.

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