UBC Theses and Dissertations
Oscillator strengths for photoabsorption and photoionization processes of feron and NO₂ molecules Zhang, Wenzhu
Absolute photoabsorption differential oscillator strengths (cross sections) for N Is and 0 Is inner shell excitation and ionization of N0₂ have been derived from the presently obtained high resolution electron energy loss spectra using dipole (e,e) spectroscopy. The N0₂ inner shell differential oscillator strength spectra are in good agreement with multichannel quantum defect theory calculations in both excitation energies and (differential) oscillator strengths. The N0₂ spectra were interpreted with the aid of the calculations. A resonance present in both the N0₂ N Is and 0 Is ionization continua was identified as excitation to an unbound molecular orbital. A consideration of the present spectra for N0₂ and earlier spectra for other molecules showed that additional prominent structures observed in previously reported N0₂ inner shell photoabsorption spectra obtained using synchrotron radiation were due to the presence of impurities. Absolute photoabsorption differential oscillator strengths for the valence shells of CF₄, CF₃CI, CF₂Cl₂ and CFCI₃ have been measured in the equivalent photon energy range up to 200 eV using dipole (e,e) spectroscopy. The present results are in good agreement with earlier reported optical measurements and electron impact measurements. The photoionization efficiencies and also the photoion branching ratios have been determined for CF₄, CF₃CI, CF₂C1₂ and CFCI₃ from time of flight mass spectra using dipole (e,e+ion) coincidence spectroscopy at equivalent photon energies ranging up to 80 eV. Absolute partial differential oscillator strength spectra for the molecular and dissociative photoions have been derived. The natures of the dipole induced breakdown pathways of CF₄, CF₃CI and CF₂C1₂ were investigated by combining the present differential oscillator strength measurements for molecular and dissociative photoionization with photoelectron data obtained in the present thesis work plus previously reported photoelectron branching ratios. On the basis of the present work, a revised set of absolute electronic state partial photoionization differential oscillator strengths for CF₄ are presented. Absolute electronic state partial photoionization differential oscillator strength spectra for CF₃CI, CF₂C1₂ and CFCI₃ in the photon energy range 41—160 eV have been derived by combining total differential oscillator strength spectra obtained in the present thesis work with photoelectron branching ratios obtained from photoelectron spectra measured using synchrotron radiation. Absolute photoabsorption differential oscillator strengths and for F Is, C Is, and Cl 2p,2s inner shell excitation and ionization of freon molecules CF₄, CF₃C1, CF₂C1₂, CFCI₃ and CCl₄ have been derived from the presently obtained high resolution electron energy loss spectra plus previously reported. Tentative assignments of the spectra were obtained using the MO picture and the potential barrier model.
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