We used recent phenomenological form factors to calculate the effect of on-shell two-pion exchange in nucleon-nucleon scattering below the two-pion production threshold. As expected, the contributions of partial wave amplitudes are all negligible. We also noticed that the relativistic spin-operator decomposition of the scattering amplitude is not unique at certain momenta and angles. / Graduation date: 2000

With the ever increasing environmental concerns in terms of the need for a vast improvement in clean energy and clean air technologies, this thesis focuses on analyzing the underlying principles that determine the activity of catalysts/sorbents for fuel cell applications and CO₂ capture using first principles based simulations with a view point to help fabricate efficient catalysts. We attempt to clarify the fuzzy concepts of existing surface-nearsurface interactions in Pd based electrocatalysts with particular attention to Pd₃Co alloy catalysts by presenting a thorough inter and intra-layer orbital analysis and bring forth the crucial role played by the surface-subsurface binding driven by the out of plane d-state interactions in determining the surface reactivity. We first decouple the effects induced by the different Pd-Pd and Pd-Co lattice parameters (lattice strain effect) from the hetero atom induced surface-subsurface interaction (we call it "interlayer ligand effect") and clearly demonstrate how enhanced surface-subsurface d [subscript xz+yz] interaction leads to an increased oxygen hydrogenation to H₂O in Pd₃Co based electrocatalysts. We then extend the concept of hetero atom induced surface-subsurface binding to a series of 3d transition metals and provide guidelines for the right choice of metals that may be potential ORR candidates. Finally, we describe the facet dependence and the effect of surface Au alloying on the surface reactivity of Pd₃Co electrocatalysts. In the second section of the thesis, we emphasize on the underlying principles of CO₂ capture by MEA and study the synergetic interplay of various factors that may lead to better CO₂ capture , also enabling efficient solvent regeneration. Though extensive studies are carried out on the most traditionally used alkanol amine MEA for CO₂ capture, there are several less studied aspects like the molecular orbital redistribution on CO₂ binding that decides the fate of the intermediate species and the role of water arrangement in assisting/hindering the progress of the reaction. We study the fundamental CO₂-amine interactions and highlight the crucial importance of alkanol-amine configuration, water arrangement and protonation/de-protonation tendencies at various basic sites in the development of the reaction. We then analyze the synergetic interplay between the inductive effect, the steric hindrance and the resonance in enhancing efficient CO₂ binding and allowing an alternative O-driven mechanism resulting into easy solvent regeneration. We believe that our efforts may help fabricate better catalysts and sorbents and help improve the existing clean energy and clean air technologies. / text

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Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Karol Lang. Vita. Includes bibliographical references.

Thesis (Doctoral?)--University of Oulu, 1987. / Includes bibliographical references.

A detailed experimental study has been made of the spin-splitting factors ℊc for magnetic Landau levels associated with conduction electrons in extremal orbits on the Fermi surface of lead. This information has been derived from the waveform of the de Haas-van Alphen (dHvA) quantum oscillations in the magnetization of single-crystal lead spheres at temperatures of about 1.2 K and with applied magnetic fields in the range 50-75 kG. A commercial spectrum analyzer has been used to provide on-line values of the harmonic amplitudes in the dHvA waveform, and the values of ℊc have been extracted from the relative strengths of the harmonics. Serious systematic errors in ℊc can arise on account of waveform distortions caused by the small and subtle difference between the externally applied field H and the magnetizing field B acting on the conduction electrons. In 1981 Gold and Van Schyndel demonstrated that these 'magnetic-interaction' distortions could be suppressed to a large extent by using negative magnetic feedback to make the induction B within the sample be the same as H (or very nearly so). This thesis describes the first in-depth application of the magnetic-feedback technique to the systematic study of any metal. Particular attention has been paid to the effect of sample inhomogeneity, and Shoenberg's treatment of the magnetic interaction in a non-uniform sample has been generalized to include magnetic feedback. This theory accounts well for many features in the experimental data, especially those which remained a puzzle in the earlier work of Gold and Van Schyndel. Experimental ℊc values are given for the first time for most of the extremal orbits on the lead Fermi surface and for high-symmetry directions of the magnetic field. Indeed these are the most detailed data reported for any polyvalent metal. The ℊc factors for the different orbits and field directions are found to span the range from 0.56 to 1.147. These large net deviations from the free-electron value ℊ₀ = 2.0023 are consequences of the strong spin-orbit and electron-phonon interactions, and an attempt has been made to separate these two contributions to the ℊ-shifts. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

published_or_final_version / abstract / Zoology / Doctoral / Doctor of Philosophy

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