Laser-Based Combustion and Trace-element Analysis

Laser spectroscopy has been utilised as a tool for combustion diagnostics and sensitive trace-element analysis.<p /> In the field of combustion analysis, a characterisation of a CH₄/N₂ - O₂/N₂ counter-flow diffusion flame has been performed using Laser-Induced Fluorescence (LIF). An absolute density profile of NO in the flame has been obtained, with concentrations up to a few tens of ppm. Temperature measurements by LIF on NO have also been performed. OH profiles were measured by both fluorescence and emission.<p /> In the trace-element analysis part of this thesis, the Tl content in rivers and lakes in the Göteborg area have been assessed to the range of a few tens of ppt by LIF in a Graphite Furnace. The Pb and Al contents of aerosols from the Norwegian Arctic have been analysed by the same technique. By the use of the LEI technique in conjunction of a rod-flame atomiser, the content of Co, Cr, Mn and Ni in NH₄F and NaF, used in the production of optical fibres, have been determined.<p /> The fundamental studies were concerned with a reassessment of branching ratios and Franck-Condon factors in NO. Vibrational and rotational collisional redistribution processes within excited states of NO and OH in a counter-flow diffusion flame were measured, where the rotational transfer in excited state of the OH molecule clearly demonstrates a ladder effect. High-lying Fe I energy levels were labelled using of a two-step laser-ionisation technique. The lifetimes of some atomic metastable states in flames have been determined.<p /> New methods for determination of the local stoichiometry in flames (by the use of atomic metastable states) and for the determination of the flow-velocity of a pre-mixed flame (using a flow-tagging technique) have been developed