Initial Preparation and Metastable Transitions in Mass Spectra

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Abstract
By variation of initial preparation of the reacting species, the detection of nonequilibrium kinetic effects is discussed for unimolecular ionic decomposition processes occurring in the mass spectrometer. A particular example, dependence of the rates of competing metastable transitions of hexyl ions on mode of preparation is studied in detail. The hexyl ions were prepared by electron impact ionization and decomposition of a variety of normal alkanes, n‐hexyl bromide and di‐n‐hexyl ether. At low electron energies (30 eV) the ratio of the competing metastable transitions is constant within experimental error. This supports the applicability of the quasiequilibrium theory of mass spectra to such processes. At higher electron energies there is a slight dependence of the ratio on parent ion mass.