Jones, Nykola Clare; (2000) Spectroscopy and dissociation dynamics of simple polyatomic molecules. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis presents results obtained from the investigation of the spectroscopy of molecules of atmospheric interest. The techniques of photoabsorption spectroscopy and electron energy loss spectroscopy (EELS) used to probe the absorption properties of these molecules are described. Using a closed cell configuration of the Daresbury laboratory molecular spectroscopy absorption apparatus (DLMSAA) the photoabsorption spectra for C2H5I, C2H5Br and the short lived OCI radical, have been recorded and are presented here. A Rydberg analysis of the spectra of the alkyl halides has been carried out and assignments have been made for the Rydberg and valence states of these molecules. A new windowless absorption apparatus is detailed which allows spectra to be taken at higher photon energies (up to 40 eV), with previous spectra limited to a maximum of 11 eV. The photoabsorption spectrum for N2O obtained using this new technique is presented and compared with that obtained using the UCL EEL spectrometer and spectra reported previously by other authors. Rydberg analysis of the spectrum has been carried out and assignments of the series converging to the first four ionisation potentials have been made. A photoelectron experiment carried out at the University of Liège and used to investigate chlorine monoxide is also described. Vibrational structure associated with the first four bands of the photoelectron spectrum has been assigned. A metastable/electron coincidence experiment (MECE) designed to investigate the dissociation dynamics of a molecule is also presented. Energy loss electrons are detected in coincidence with metastable excited state neutral fragments formed via dissociative excitation in an electron impact process. This technique is used to learn more about the energy levels in the parent molecule.

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