A proton polarimeter has been constructed at TRIUMF, with design specifications intended to measure the polarization of protons over an energy range of 100 MeV to 300 MeV. It was built as the principle detector in an experiment to determine three spin-transfer parameters of the fundamental π⃗d → p⃗p reaction. In this thesis, some theoretical and experimental design aspects of the spin-transfer measurement are discussed. The intent of this thesis is to describe an experiment¹ which measures the polarization of protons emitted from the πd→ p⃗p reaction, using an unpolarized target². The sole purpose of this experiment is to demonstrate that our polarimeter and general apparatus are capable of identifying the πd → pp events from a large background presence, and that the systematic errors associated with the polarization extraction have been identified. To this extent, the system is ready to produce the proton polarization required for the spin-transfer measurements. ¹This experiment is identical in all respects to the spin-transfer experiment, except that here, the target is unpolarized. ²The polarization of the protons is well know from the analyzing power, An₀, of the time reversed p⃗p → dπ reaction. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The positive muon is an unstable (Tµ =2.2µsec) particle but one with properties very similar to the proton from a chemical and atomic physics point of view. It has, however, a mass only 1/9 that of the proton, a fact which makes it ideal for studying any mass dependence in chemical and physical phenomena. The µSR and MSR techniques have been utilized to study various relaxation phenomena that occur in the gas phase when the muon or muonium (the muon and electron bound state analogous to the hydrogen atom) interacts with its environment. The fraction of muons that thermalize as muonium has also been measured. It was found that 83% of the muons stopping in n₂ formed muonium, the remainder staying in the charged state. Other gases investigated were H₂ (61 %) , CH₄ (86%), NH3(90%), He(0%), Ne(4%), Ar(74%), Kr(100%) and Xe100%). The amplitude of the signal was found to be strongly pressure dependent and this has been explained in terms of the thermalization time of the muons in these gas targets. Various gas mixtures were also studied where it was found that relaxations of the µSR signal occured as a function of added reagent gas concentration. This phenomena has been attributed to reactions of muon molecular ions with the reagent gas, forming muonium thermally. This represents the first reliable measurements of muon relaxation in the gas phase. Evidence is presented indicating that such reactions occur from the first vibrational state of these muon molecular ions. The systems studied and their room temperature rate constants The spin exchange interactions of muonium with NO and 0₂ were also studied as a function of temperature in the range 295K to 478K. The measured rate constants exhibit a temperature dependence consistent with T ½ and hence a constant spin exchange cross section. The temperature averaged spin exchange cross sections found are: for Mu+O₂, 6~SE=9.0±1x10⁻¹⁶cm² and for Mu+NO, 6se = 1 0 . 5±1 x ⁻¹⁶cm². These values are essentially the same as the cross sections found for hydrogen atom spin exchange with the same molecules, in qualitative agreement with current theoretical predictions. / Science, Faculty of / Chemistry, Department of / Graduate

An orbital dependent local spin density-functional (LSD) scheme with a generated exchange, the LSD GX scheme, has been developed based on the correct normalization conditions of an electron gas. This scheme contains no adjustable parameters; the B$ sb1$, B$ sb2$ and $ alpha sp lim$ are constant for all atoms once the shape of the Fermi hole is chosen. These parameters are rigorously calculated using an unspecified Fermi hole correlation factor and they give an exchange density which reduces exactly to the homogeneous free electron gas one at the high electron density limit. / The LSD GX exchange density is corrected for self-interaction (SI) by splitting the total Fermi hole correlation factor into pure-exchange and self-interaction holes. / These new LSD and SI corrected schemes are compared to each other. They also compare very well theoretically and numerically (total energies and eigenvalues) with other local schemes current in the literature. / New equations for the IP and electronegativities of the atoms in these local schemes are derived which give good results.

No description available.

This dissertation is organized into eight chapters, each focusing on different aspects of Nuclear Magnetic Resonance (NMR) and Spin Exchange Optical Pumping (SEOP), with an emphasis on enhancing nuclear spin polarization and the development of advanced hyperpolarization systems. Chapter 1 introduces NMR, tracing its history and explaining key concepts like nuclear spin, magnetic moment, and fundamental interactions such as the Zeeman effect and chemical shift. The chapter emphasizes NMR's significance in fields like chemistry, physics, biology, and medicine. Chapter 2 explores techniques to enhance nuclear spin polarization, crucial for improving NMR sensitivity. A key concept is hyperpolarization—the creation of high nuclear spin polarization that is well above the weak polarization normally attained at thermal equilibrium conditions. This chapter briefly covers brute-force methods and non-equilibrium approaches like Dynamic Nuclear Polarization (DNP), Parahydrogen-Induced Polarization (PHIP), Signal Amplification by Reversible Exchange (SABRE), and Spin-Exchange Optical Pumping (SEOP), each with distinct advantages, challenges, and applications.Chapter 3 delves into SEOP, given its central role underlying the work in this dissertation. This chapter details SEOP’s historical development, theoretical background, and key mechanisms underlying optical pumping and spin-exchange collisions. It also discusses the practical importance of various experimental aspects, including cell temperature and alkali metal vapor density, as well as emphasizing the role of nuclear spin relaxation in optimizing NMR and MRI applications. Chapters 4 and 5 provide key background information concerning relevant technologies underlying SEOP. First, Chapter 4 examines laser light sources essential for SEOP, focusing on high-power laser diode arrays (LDAs). It also compares various accompanying laser technologies, highlighting Volume Holographic Gratings (VHGs) as an efficient solution for spectrally narrowing LDA output, which is crucial for improving the efficiency of SEOP. Chapter 5 then shifts focus to clinical-scale stopped-flow xenon-129 hyperpolarizers, covering both first- and second-generation developments of this technology. The first-generation design achieved near-unity polarization and demonstrated some automation but encountered challenges in complexity and temperature regulation. The second-generation design improved systems integration, performance, and robustness, making significant strides in clinical applicability. Building from these developments, Chapter 6 details the development of a third-generation stopped-flow xenon hyperpolarizer designed to overcome the limitations of previous designs. Innovations include a compact, mobile structure, an advanced solenoid electromagnet for improved magnetic field homogeneity, and an aluminum heating jacket for precise control over SEOP cell temperature. These enhancements support hyperpolarized 129Xe production for clinical applications such as lung imaging. The chapter also discusses the construction process, operational principles, and SEOP studies conducted to maximize the hyperpolarizer's efficiency and output. Chapter 7 explores the hyperpolarization of a different isotope of xenon—131Xe (a stable quadrupolar isotope)—for neutron-science applications. Following efforts achieving record levels of bulk production of HP 131Xe (albeit still at relatively small scales), this effort moves to scaling up the process in order to investigate the creation of HP 131Xe targets within aluminosilicate (GE180) cells in support of neutron optics experiments investigating time-reversal symmetry violations. As a result of this work, it was possible to create and ship such cell targets for neutron beam experiments in Jülich, Germany. Finally, Chapter 8 presents initial efforts concerning the development of a next-generation modular laser system for SEOP in clinical and fundamental physics applications. Addressing limitations in current laser systems, the new design emphasizes modularity, cost-effectiveness, and improved SEOP efficiency, with preliminary results demonstrating significant advancements and promising enhancements in laser performance, laying the groundwork for future developments.

The high-spin states of the nucleus 64Ge have been investigated using the GASP and the EUROBALL arrays of high-purity germanium detectors. In order to achieve the required experimental sensitivity, special selecting devices were used, namely a highly efficient array of liquid scintillators to detect neutrons and the ISIS Si-ball to detect light charged particles, which has been developed in the present work. A detailed decay scheme for 64Ge has been deduced, assigning spins and parities to the levels through a Directional Correlation from Oriented states analysis, an Angular Distribution analysis and a Polarization Correlation from Oriented states analysis. The character of an intense 1665 keV transition, previously reported as a stretched electric dipole with a small multipole mixing ratio, has been established as an electric dipole with a large multipole mixing ratio. The electric dipole strength has been measured using EUROBALL coupled to an early implementation of the EUCLIDES Si-ball and with the Koln plunger device, allowing an experimental estimate of the isospin mixing probability in 64Ge.

Call number: LD2668 .T4 1985 J665 / Master of Science

Thesis (Ph. D.)--University of Chicago, Department of Chemistry, 2002. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (p. 224-236).

NMR is a powerful analytical spectroscopic tool used to perform detailed studies of structure and dynamics of molecules in solution. However, despite NMR's excellent spectral sensitivity, most NMR methods suffer from low detection sensitivity. This low detection sensitivity results largely from extremely small (Boltzmann) nuclear spin polarization at thermal equilibrium--in even the strongest of magnets. This dissertation focuses on selected research areas that maybe used to combat the limitations presented by NMR and measure weak spectral responses with atomic-scale precision. In particular, these methods involve the use of laser-polarized xenon, liquid crystals, and polarization transfer (cross-polarization) techniques to enhance NMR sensitivity and/or measure weak interactions. The potential use of these tools to study host-guest interactions is of particular interest. In certain systems the sensitivity problem of conventional NMR/MRI can be overcome by applying optical pumping (OP) methods to enhance nuclear spin polarization. For instance, OP of noble gases (such as xenon) is employed to dramatically increase their nuclear spin polarization by transferring angular momentum of laser light to electronic and then nuclear spins. Next, cryptophane complexes are ideal choices for fundamental studies of prototypical host-guest interactions. Of general interest when studying host-guest interactions is how (1) physical confinement at the nanoscale and (2) interactions between guest and host may affect the properties, dynamics, interactions, and/or reactivity of a trapped molecule and the host/guest complex as a whole. As a more specific example, we are interested in probing host-guest dynamic coupling, which refers to the relative motion of the guest within the host, determined by the relative sizes and geometries--as well as the interactions involved. With the development of new NMR methods and techniques, we hope to gain insight into mechanisms that underlie complex formation by probing the structures, dynamics and energetic contributions involved in ligand binding, where molecular contributions such as: orientational and motional freedom of the guest; and structure, dynamics, and ordering of the host can influence the behavior of inclusion complexes.