Thesis (Ph. D.)--California Institute of Technology, 1978. UM #78-15,971. / Advisor names found in the Acknowledgments pages of the thesis. Title from home page. Viewed 01/19/2010. Includes bibliographical references.

A comparative study has been made of Penning ionization (He*(2¹S) and He*(2³S)) and photoionization (He(584 Å)) of twenty-three atoms and molecules (Ar, Kr, Xe, H₂, HD, D₂, N₂, CO, NO, 0₂, C0₂, COS, CS₂, N₂0, S0₂, N0₂, NH₃, CH₃CI, CH₃Br, CH₃I, CH₄, C₂H₄ , C₂H₂) employing the techniques of high resolution electron spectroscopy. Electron spectra from mixed rare gas systems, at higher pressures, have also been examined and interpreted on the basis of fast neutral-neutral interactions. / Science, Faculty of / Chemistry, Department of / Graduate

Energy loss spectra of 2.5 keV electrons, scattered by molecular targets through small angles, have been studied in the regions of the respective carbon, nitrogen, oxygen and fluorine K-edges and the sulfur LII,III edges. Electron energy loss spectra for diatomic, triatomic and polyatomic molecules have been studied. Discrete excitations have been interpreted in terms of the promotion of the respective K-shell electron to unfilled valence molecular orbitals and Rydberg orbitals. Most spectra show considerable structure above the respective K-edge, in addition to the normal K-continuum. This structure represents the simultaneous transitions of a K-shell and valence shell electrons (i.e. shake-up and shake-off events following the creation of an inner hole). In the case of molecular nitrogen and carbon monoxide, a simple core model was shown to provide an accurate description for the K-shell excited molecule. On the basis of this model, excitation and ionization energies for some exotic chemical species have been predicted from the relative energies observed in the K-shell energy loss spectra of a number of molecules. The agreement between the estimated (core analogy) and observed K-shell excitation energies for larger molecules is less satisfactory, possibly because of the large changes in molecular geometry which occur as a result of an election promotion. Finally, the carbon K-shell energy loss spectra of carbon disulfide, carbonyl sulfide and carbon tetraf1uoride show features which are possibly associated with the existence of an effective potential barrier in these molecules. / Science, Faculty of / Chemistry, Department of / Graduate

No description available.

This thesis reports the study of molecular and electronic structure of iridium containing diatomic molecules using the technique of laser ablation/reaction with free jet expansion and laser induced fluorescence (LIF) spectroscopy. The iridium containing diatomic molecules studied in this research are iridium phosphide (IrP), iridium boride (IrB) and iridium oxide (IrO). These molecules were produced by the reaction of Ir atoms ablated by a pulsed neodymium-doped yttrium aluminium garnet (Nd:YAG) laser and 1% PH3, 0.5% B2H6 and 6% N2O gases to produce IrP, IrB and IrO molecules respectively. Pulsed tunable lasers: a dye laser and an optical parametric oscillator (OPO) laser system were used to cover the spectral region between 390 and 650 nm in obtaining electronic transitions of the iridium containing diatomic molecules. The recorded electronic spectra of IrP, IrB and IrO molecules yields information on the bond length and electronic structures. For the IrP molecule, five electronic transitions, namely the [21.2] 3Σ+ – X1Σ+, [21.7]1Σ+ – X1Σ+, [23.6] 0+ – X1Σ+, [23.7] 0+ – X1Σ+ and [23.9] 0+ – X1Σ+ transitions, have been recorded and analyzed. The bond length, r0, and the ΔG1/2 of the ground state of 193IrP molecule was determined to be 1.9928? and 569.77 cm-1 respectively. For the IrB molecule, four new electronic transition systems, namely the [18.8]3Δ3 – X3Δ3, [21.1]3Φ4 – X3Δ3, [22.8]3Φ3 – X3Δ3 and [22.4]1Φ3 – a1Δ2 transitions, were observed and analyzed rotationally. The bond lengths, r0, of the upper states of 193IrB were determined to be within 1.72 and 1.80?. For the IrO molecule, five electronic transitions from two different lower states were recorded and analyzed, namely the [17.6] 2.5 – X2Δ5/2, [17.8] 2.5 – X2Δ5/2, [21.5] 2.5 – X2Δ5/2, [22.0] 2.5 – X2Δ5/2 and [21.9] 3.5 – Ω = 3.5 transitions. The ground state of IrO has been confirmed to be 25/2. The bond length, r0, and the ΔG1/2 of the ground state of 193IrO molecule was determined to be 1.726 A and 900.00 cm-1 respectively. For all the transitions observed, rotationally-resolved transition lines were fit to theoretical models to obtain molecular constants for both the upper and lower electronic states. Typical molecular transition linewidths obtained was larger than 0.1cm-1, which is likely to be due to unresolved hyperfine structure in the rotational lines. In addition, the observation of isotopic spectrum confirmed the assignment of vibrational quantum number. Molecular and electronic structures of these iridium containing diatomic molecules were discussed using a simple molecular orbital theory. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

abstract / Physics / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2009. / Title from title screen (site viewed July 6, 2010). PDF text: x, 133 p. : ill. (some col.) ; 3 Mb. UMI publication number: AAT 3366064 . Includes bibliographical references. Also available in microfilm and microfiche formats.

No description available.

The binding energies and momentum distributions of all of the valence orbitals of (CH₃)₂O, PH₃, CH₄ and SiH₄ have been measured by high momentum resolution electron momentum spectroscopy. The binding energy spectra have been compared to Green's function and configuration interaction calculations from the literature and with new calculations performed in collaboration with co-workers at Indiana University and Universitat Braunschweig. For PH₃, CH₄ and SiH₄, near Hartree-Fock limit calculations of the momentum distributions and very accurate calculations of the ion-neutral overlap using MRSD-CI wavefunctions to describe the ion and target have been performed in collaboration with co-workers at Indiana University. Good agreement is obtained between the (CH₃)₂O measurements and the momentum distributions calculated from relatively simple wavefunctions, except in the case of the outermost orbital. The effects of diffuse and polarization functions in the basis sets, and also the influence of molecular geometry, have been investigated. Comparison of the momentum distributions of the outermost orbitals of H₂O, CH₃OH and (CH₃)₂O demonstrates a delocalization of charge density with methyl substitution. The measured momentum distributions of PH₃, CH₄ and SiH₄ are compared with near Hartree-Fock limit calculations as well as ion-neutral overlap calculations in which the ion and neutral wavefunctions are described by multireference, singly and doubly excited, configuration interaction calculations. In each case, the experimental results are well modelled by the near Hartree-Fock limit calculations, and there is little difference between the Hartree-Fock limit and ion-neutral overlap calculations. A significant splitting of the 4a₁ (inner valence) pole strength is observed for PH₃, but the inner valence strength is largely contained in the main peak for both CH₄ and SiH₄. Green's function calculations quantitatively reproduce these results. Ion-neutral overlap calculations using MRSD-CI wavefunctions to describe the ion and target have been performed for HF, HCl, Ne and Ar. These are compared with previously published EMS measurements of the momentum distributions. Very poor agreement between theory and experiment is obtained for HF and HCl. The theoretical and experimental results for all of the hydrides CH₄-HF and SiH₄-HCl as well as Ne and Ar are reviewed. / Science, Faculty of / Chemistry, Department of / Graduate