Trace Analysis Using Laser Ablation Initiated Resonant Ionisation Mass Spectrometry

McCombes, Paul Thomas (1991) Trace Analysis Using Laser Ablation Initiated Resonant Ionisation Mass Spectrometry. PhD thesis, University of Glasgow.

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This thesis deals with the practical aspects of the development and use of a resonant ionisation mass spectrometer. The first chapter gives an outline of the ideas and the applications of resonant ionisation mass spectrometry (RIMS), together with a brief historical overview of the method, showing its development in the last twenty years. The second chapter deals with the theoretical aspects of resonant ionisation spectroscopy (RIS). Firstly time dependent perturbation theory is used to demonstrate how the selectivity and sensitivity of the method come about. Next the derivation of rate equations for a simple system, a practical way of analysing RIMS ion yields, is shown. Causes of broadening of transitions are then described. Non-linear optics and the theoretical aspects of laser ablation are then discussed. Chapter 3 deals with the instrumentation and describes the equipment used. The mass spectrometer was designed and assembled in Glasgow and constructed by Kratos Analytical. This chapter details the improvements that have been made to the original design. Further enhancements that are possible but not implemented are given in chapter 8. Chapter 4 describes the development of the computer software. This software is used to control the data acquisition hardware and for subsequent analysis of the data. The software was written exclusively by the author. Chapter 5 presents some of the earlier results from the instrument. The author, together with Dr Mike Towrie and Dr Adrian Land, was responsible for the acquisition of these results Chapter 6 examines in detail the laser ablation process. Laser ablation is used to evaporate samples to produce a flux of neutrals leaving the surface. It is the primary evaporation source used at Glasgow and it is very poorly understood, both in terms of underlying theory and some phenomenological aspects of it. For the optimal operation of the instrument the process of neutral production must be well characterised. The calcium ablation work presented was performed by the author, Dr M Towrie and Dr A Land. The gold and lead ablation work was the exclusive work of the author. The work on aluminium and NIST steel was performed by Mr I Borthwick and the author. Chapter 7 presents work on trace analysis of gold using RIMS. This work involves the detection of trace amounts of gold in a copper matrix. Other resonant schemes will be discussed. All work in this chapter is the sole work of the author. Chapter 8 gives conclusions about the viability of the RIMS method in the field of trace analysis, together with a discussion of possible improvements in the instrument and the methodology. Appendix A contains information on the physical characteristics of gold. Appendix B gives details of field inverting optics which were designed by the author. A design of this type is expected to improve the performance of the instrument described in this thesis.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Applied physics, Optics
Date of Award: 1991
Depositing User: Enlighten Team
Unique ID: glathesis:1991-78240
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 15:35
Last Modified: 30 Jan 2020 15:35

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