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Absolute photoabsorption and photoionization studies of halogen containing molecules by dipole electron impact methods

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Title: Absolute photoabsorption and photoionization studies of halogen containing molecules by dipole electron impact methods
Author: Olney, Terry N.
Degree Doctor of Philosophy - PhD
Program Chemistry
Copyright Date: 1996
Abstract: Dipole (e,e) spectroscopy has been used to determine absolute photo-absorption oscillator strengths (cross-sections) for the discrete and continuum electronic transitions of CH₃F, CH₃CI, CH₃Br, CH₃I, and BrCN. These data have been obtained at low resolution (1 eV fwhm), spanning the visible to soft X-ray equivalent photon energy regions (4.5 to 450 eV), and at high resolution (0.05 to 0.15 eV fwhm), in the valence and inner shell (Br 3d; I 4d; C Is (BrCN); N Is) regions. The absolute photoabsorption oscillator strength scales were established using either the Thomas-Reiche-Kuhn sum-rule (S(0)) or an S(-2)-based sum-rule normalization technique. To confirm the global accuracy of the dipole (e,e) photoabsorption oscillator strength data, an assessment of the absolute scales of previously published dipole (e,e) photoabsorption spectra 51 atoms and small molecules is made by deriving static dipole polarizabilities using the S(-2) sum-rule. Alternative methods of absolute scale determination for photoabsorption spectra using S(-2)-based normalization with dipole polarizabilities are also considered. Various dipole oscillator strength sums S(u) (u=-l to -10) and L(u) (u= -1 to -6) are evaluated using the previously published, and presently reported, dipole (e,e) measure-ments. It is also shown that normal Verdet constants and values of the rotationally averaged C₆ (A,B) dispersion coefficients can be reliably obtained either directly from the measured oscillator strength spectra or from approximations which require only values of the dipole sums S(u) and L(u) reported here. Quantitative aspects of the molecular and dissociative photoionization are reported in he valence shells of CH₃F and CH₃C1, and the valence shells and low energy inner shells (Br 3d and I 4d) of CH₃Br, CH₃I and BrCN, have been studied using dipole (e,e-t-ion) spectroscopy. Time-of-flight mass spectroscopy was used to determine the absolute partial oscillator str- engths for the molecular and dissociative photoionization channels of the methyl halides and BrCN. In other work synchrotron radiation photoelectron spectroscopy measurements made by Dr. Cooper, Dr. Chan and Dr. Tan were used to determine the absolute partial photoionization oscillator strengths for the production of the electronic states of CH₃F+ , CH₃C1+ and CH₃Br+ . These measurements together were used to provide detailed quantitative in-formation on the dipole-induced breakdown pathways of the methyl halides and BrCN under the influence of VUV and soft X-ray radiation.
URI: http://hdl.handle.net/2429/6132
Series/Report no. UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/]

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