Award Date

1-1-2007

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Committee Member

Dennis W. Lindle

Number of Pages

167

Abstract

The x-ray emission of CCl4, CFCl3, CF2Cl 2, and CF3Cl has been observed by measuring the polarized Cl K-L and K-V fluorescence in the gas phase. Experiments were conducted at the Advanced Light Source in Berkeley CA using a polarization sensitive x-ray emission spectrometer. In both energy ranges, the measured x-ray peak widths and energy dispersion are dependent on the initial photon energy and the final state lifetime broadening and can be described with established theoretical models. The first measurement of a negative energy dispersion is reported here where the energies of the emitted peaks are decreasing with increasing photon energy close to the 4 p Rydberg In this case, the emitted photon's energy is dependent on vibrational excitations of several intermediate states. 1n the K-L energy range, there are significant deviations from the statistical 2:1 spin-orbit ratio that can he attributed to molecular field effects. The extent of the molecular field effects is dependent on the symmetry of the molecule and the orientation of the orbitals involved in absorption and emission with the emission in the parallel direction showing the largest effects. In the K-V energy range, the x-ray emission above the ionization potential (IP) was observed to be anisotropic in CF2Cl2 and CCl4 and largely isotropic in CF3Cl. This difference above the IP has been attributed to nondipole effects where vibronic coupling between near degenerate states (CI ls orbitals) can open decay channels otherwise not seen when the dipole approximation holds; this explains why anisotropy is seen in molecules with multiple CI atoms.

Keywords

Chlorine; Chlorofluoromethanes Chlorine; Chlorofluoromethanes; Edge; Emission K Edge; K Edge; Polarized; Ray; Spectroscopy

Controlled Subject

Chemistry, Physical and theoretical; Molecular dynamics

File Format

pdf

File Size

3983.36 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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