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Title: Resonance ionisation mass spectrometry of trace elements in metallic and organic host matrices
Author: Jones, O. R.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1995
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In this work, sputter initiated resonance ionisation mass spectrometry has been used for quantitative analysis of trace amounts of elements in both metallic and organic host matrices. In parallel with the experimental work, theoretical methods have been developed to describe both the interaction of the laser radiation with the plume of sputtered particles and the processes involved in resonance ionisation. On the experimental side, general one-colour, two-step resonance ionisation schemes were demonstrated, using a reflectron type time-of-flight mass spectrometer combined with a duoplasmatron primary sputter ion source and a Nd:YAG pumped dye laser system. Timing electronics were developed to precisely synchronise the pulsed laser system to the sputter process and the mass spectrometric analysis. For metal matrices, the elements titanium, chromium, iron, nickel and molybdenum were probed in the 290-300nm wavelength range. The detection of an enhanced molybdenum signal at 294.421nm is believed to be the first resonance ionisation signal to have been obtained for this element. Aluminium was probed in the 305-310nm wavelength range. For organic matrices, the feasibility of using spatially resolved resonance ionisation mass spectrometry for the analysis of potentially toxic element accumulation in neural tissue was investigated. In particular it was shown that aluminium, which is linked to brain disorders such as Alzheimer's disease, could be detected in brain tissue at concentrations of around 100ppm, with a detection limit of about 3ppm using the current set-up. On the theoretical side, the use of a quantum mechanical density matrix approach in describing the process of resonance ionisation was shown to be more generally applicable than a simple rate-equation or Schrödinger equation approach. In particular, the saturation of the resonant and ionisation steps, and the power broadening of the resonant transition at high laser fluences were investigated, with satisfactory agreement found between theory and experiment in both cases.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available