Double-focusing mass spectrometer description

In the following sections of this article, we describe the principles of ionization cross-section measurements, including a brief description of the fast-beam apparatus and the high-resolution double-focusing mass spectrometer employed in the present studies. A comprehensive review of semiempirical calculations of total ionization cross sections is given. Comparisons between these calculated cross sections and the experimental results are presented. The decomposition of the various molecules in a low-temperature plasma is discussed on the basis of the measured ionization-cross-section data, and comparisons are made with the results of in situ plasma diagnostics studies using mass spectrometric techniques. 

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