Date of Award
Doctor of Philosophy
Dr. Nora Berrah
Dr. Thomas Gorczyca
Dr. John Tanis
Dr. Emanuel Kamber
Interaction between synchrotron radiation with inner-shell electrons is a fundamental method to study the structure and dynamics of atoms and molecules. This thesis, under the guidance of Dr. Nora Berrah, concentrates on the study of the interaction between soft x-ray photons with Ar atoms and HBr moleculeswith time-of-flight (TOF) electron spectrometers and two-dimensional photoelectron spectroscopy (2DPES). Both of the experiments were performed on theAtomic, Molecular and Optical Physics undulator beamline at the Advanced Light Source at Lawrence Berkeley National Laboratory.
The argon study focused on photoelectron recapture when the 2p electrons are ionized just above the thresholds of the two [special characters omitted] components. From our 2DPES maps, we obtained an experimental recapture curve at the [special characters omitted] threshold as a function of photon energy.The curve is derived by extracting all the reemission photoelectrons from a specific recaptured intermediate excited state and subtracting the contributions from the 2p -1 nl resonances and the recapture at the [special characters omitted] threshold. The experimentally obtained curve is in good agreement with both our semi-classical calculation result and the calculation performed with quantum-mechanics by Tulkki et al. [Phys. Rev. A 41, 181 (1990)].
The HBr molecule study aimed mainly at measuring the atomic decay channel from the [special characters omitted] resonances. At these resonances, therepulsive characteristics of the antibonding orbital cause the molecules to dissociate, resulting in both atomic Auger decay and molecular Auger decay. We separate the two resonances and find that the peak positions are at 70.89 and 71.92 eV, respectively. Some atomic lines are assigned based on their kinetic energy positions. We find that the profiles of the atomic Auger lines on the photon energy scale are not symmetric. The atomic line pair, produced from one of the two resonances and decaying to the same final Br+ state, have approximately the same angular distribution parameters, β. The intrinsic anisotropy parameters, α2, of the atomic lines, derived from the β values, are determined and are found to be similar to those of the equivalent Auger lines in krypton. Thealignment parameters A 20 for the two resonances [special characters omitted] are found to be -0.64(5) (2D5/2) and -0.60(5) (2D3/2), respectively, which are in good agreement with the theoretical value of -0.74 predicted for the 2D5/2 resonance [Kabanchnik et al., J. Phys. B 31, 4791 (1998)].
Feng, Ximao, "Photoexcitation and Photoionization of the Argon Atom and the Hydrogen Bromide Molecule" (2005). Dissertations. 1029.