The spectroscopic study of simple polyatomic molecules by synchrotron and laser irradiation

This thesis describes the spectroscopic study of simple poly-atomic molecules, for example NO and Cl2O by UV radiation derived from synchrotron and laser sources. Synchrotron studies were carried out at the Daresbury Laboratory Synchrotron Radiation Source, and the laser studies performed at University College London. The thesis is composed of six chapters. The first chapter discusses molecular structure; UV absorption of photons by simple molecules and describes the modern techniques of Resonance Enhanced Multi Photon Ionisation (REMPI) and Laser Induced Fluorescence (LIF) processes. Chapter two describes the apparatus and the experimental techniques developed during this project at the Daresbury Laboratory Synchrotron Radiation Source. Details are given on the different photoabsorption cells that were built and used, as well as details of synthesis plants used to create short lived molecules of particular importance to atmospheric chemistry, for example N2O5. Chapter three gives a full description of the laser system constructed to study REMPI and LIF processes. The data collection and experimental methodology of the final experimental configuration to study REMPI phenomena is also detailed. Chapter four describes the results obtained by photoabsorption studies for the atmospheric nitrogen and chlorine oxides (Cl2O, N2O5 and ClONO2) Chapter five gives an overview of the results obtained by photoabsorption studies of Polycyclic Aromatic Hydrocarbons. Chapter six presents conclusions of the current work and discusses future experiments that may be undertaken in the apparatus developed during this PhD program