Some aspects of metastable ion peak shapes

• Main Author: Howells, S.
• Published: Swansea University 1980
• Subjects: 543.5
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637317

The thesis is concerned with shapes of metastable peaks that are produced as the result of the release of translational energy that occurs when a metastable ion undergoes fragmentation in one of the field-free regions of a mass spectrometer. The work was performed partly on a commercial mass spectrometer manufactured by VG-Micromass Ltd (the ZAB-2F) and partly on a mass spectrometer constructed as part of the research from parts manufactured by Varian-Mat GmbH. Chapter I gives a brief survey of the available methods for studying metastable ions in mass spectrometers. Chapter II gives details of the mass spectrometer constructed. It discusses the design considerations, gives details of the various component parts and discusses the effects upon the performance achieved, in terms of energy resolution, of the slit sizes and fringing fields. The overall performance of the instrument is then assessed. Chapter III explains the relationship between translational energy release during ionic fragmentation and the detailed shape of the metastable peak. It discusses how the slit shapes (both width and height) affect the discrimination of the instrument against productions with components of velocity perpendicular to the original direction of motion and stresses the importance of angular collimation of the reactant ion beam. Chapter IV illustrates how such factors as instrument stability and incorrect setting of the controls can also affect the shapes of the metastable peaks observed. Chapter V extends the study to include ionic fragmentation reactions induced by a collision gas and Chapter VI gives further details of the experimental techniques employed. The work is illustrated by many examples of peak shapes obtained for the reaction of polyatomic organic ions and the information that can be obtained from these shapes is assessed.