Comments on accuracy in mass-spectrometric gas analysis

Abstract

Analysis of mass spectra from gases or gas mixtures has become a routine procedure in modern vacuum technology. The interpretation of these spectra, however, is straightforward only in very simple cases. In practical work, especially if oxygen-bearing gases dominate the spectrum, the defolding of peaks at interfering mass numbers turns out to be difficult, even if the cracking patterns are known precisely and do not change during the measurement. Changes in the cracking patterns may be caused by reactions at the hot filament, by sorption processes, by ESD, etc. Although the basic aspects of these disturbances are fairly well known, there is little knowledge about their influence on the accuracy of the calculated gas composition. In this contribution we give a discussion of experimental results (achieved with a commercial RGA) concerning the influence of disturbing effects on the calculated gas composition, with special emphasis on mixtures of CO and CO 2.