It was the purpose of this investigation to study the hyperfine structure of the β-unstable isotopes of samarium using the atomic beam magnetic resonance technique. A brief review is given of the nuclear and atomic theory necessary for the interpretation of the experiments. The hyperfine interaction constants (Mc/sec) for Sm153, and the nuclear moments inferred from them, are summarized below: A1 = - 2.100(5) B1 = 289.042(4) A2 = - 2.573(6) B2 = 306.521(21) C2 = - 0.0003(9) A3 = - 3.115(4) B3 = 165.824(20) C3 = - 0.0087(12) μI = - 0.021(1) n.m. Q = 1.1(3) barns From the quadrupole moment it follows that the nuclear deformation δ = 0.25(5). The magnetic moment disagrees with the predictions of the Nilsson model for either spin 3/2 state with which the Sm153 ground state might be associated. Also determined was the spin of Sm155. The result, I = 3/2, confirms the assignment from the less direct evidence available from radioactive decay studies. The more extensive measurements necessary to determine the moments were not attempted. / Thesis / Doctor of Philosophy (PhD)

The design and construction of a coincidence spectrometer and its application to the study of the decay of Os¹⁹³ are presented. / Thesis / Doctor of Philosophy (PhD)

<p> Concretions in a zone about 4 m. below the Tichenor Limestone formed just below the sediment water interface. Their growth was initiated about an organic-rich fossil cluster and was probably completed before they were more than 5 to 8 m below the sediment surface. Chemical products of organic decay, notably bicarbonate ions and ammonia, diffused outward, raising the pH and precipitating calcite from connate waters already nearly saturated with respect to calcium carbonate. These conclusions derive from the shape of the concretions, from their relation to the enclosing shales, and from their overall structure , particularly the position of pyritic fossil clusters. The relative volumes of soluble material (calcite) in the concretions are consistent with relative pore volumes through the upper 5 m. of recent, fine-grained, clayey sediments. The postulated genetic sequence agrees with recent work on carbonate diagenesis. Restriction of the concretions to discrete layers was most probably due to a widespread comnbination of high rates of organic productivity, high rates ·of sedimentation, and low rates of water circulation, that lasted a short period of time and resulted in the rapid burial.of much undecomposed organic material. </p> / Thesis / Master of Science (MSc)

<p> Though Neutron Activation Analysis is one of the most sensitive multielement analysis methods, Compton interference in complex sample matrices usually presents a problem when choosing irradiation and decay times for analysis. While various scientists have attempted to solve the problem, the approaches taken to date have the drawbacks of either requiring standard spectra of the sample components or not giving the optimum times automatically and simultaneously. The purpose of this thesis was to find a method to automatically and simultaneously obtain the optimum times for Instrumental Neutron Activation Analysis using the Modified Simplex Method to evaluate the best figure of merit calculated from an advance predicted spectrum of the sample.</p> / Thesis / Master of Science (MSc)

<p> Fine structure in thermal neutron (n, α) reactions has been studied for 149Sm, 147Sm, and 143Nd by means of an instrument called an electrostatic particle guide. This device, which was designed to eliminate the problems of background and low energy tailing in (n,α) spectroscopy, is described in detail. Alpha decay has been observed from thermal neutron capture states to levels in the daughter nucleus to greater than 2 MeV excitation. Cross sections and alpha energies are presented for each transition and as well, the alpha decay schemes for 146Nd, 144Nd, 140Ce. Experimental reduced widths have been calculated and are discussed in terms of Mang's theory of alpha decay. Evidence is presented for the (n, γα) process in the 143Nd (n,α) 140Ce reaction. </p> / Thesis / Doctor of Philosophy (PhD)

<p> A variety of experiments has been performed in order to establish and identify the states in 191Ir and 193Ir. From radioactive decay, the energies and intensities of the gamma rays and internal conversion electrons have been measured with high precision using Ge(Li) detectors and the Chalk River π√2 spectrometer. A series of gamma-gamma coincidence experiments were performed using Ge(Li) detectors. The gamma rays following Coulomb excitation of 191Ir and 193Ir were also measured with Ge(Li) detectors. In addition, (3He,d) and (α,t) transfer reactions were performed and the reaction products analyzed by means of an Enge split-pole spectrograph. From these data, the energies, spins, parities and spectroscopic factors for the states in 191Ir and 193Ir have been established and interpreted in terms of the Nilsson model with band mixing.</p> / Thesis / Doctor of Philosophy (PhD)

Techniques of beta- and gamma-ray scintillation spectroscopy have been applied to a study of the decay radiations from 92.6-min La142. Several new gamma-ray transitions have been discovered and a gamma-gamma coincidence matrix has been established. Nine beta groups have been identified and evidence is presented substantiating the assignment of a first-forbidden unique character to the ground-state beta transition. Angular correlation studies have been performed on some of the gamma cascades. A decay-scheme based on the experimental results is discussed and some spin assignments are made. Some features of the decay modes are interpreted within the context of contemporary ideas about nuclear structure. / Thesis / Doctor of Philosophy (PhD)

<p> Twenty-two energy levels of 105Ru populated in the beta decay of 105Ru have been determined. The internal conversion coefficients of the eighteen strongest transitions were measured using a magnetic spectrometer and were used to obtain their multipole assignments. The energies and intensities of seventy gamma rays were measured using germanium detectors and scintillation counters. Gamma-gamma and beta-gamma coincidence measurements carried out with magnetic spectrometers, NaI(Tl) and Ge(Li) detectors were used with these energy measurements to establish a decay scheme. An interpretation of the decay scheme in the light of current nuclear models was attempted.</p> / Thesis / Doctor of Philosophy (PhD)

We obtain an upper bound for decay rate of p-adic oscillatory integrals of with analytic phase function and constructible amplitude map. / Thesis / Doctor of Philosophy (PhD)

Metastable states are classically stable at zero temperature but can decay due to quantum tunneling. The rate of this process is exponentially small and it may be computed in Euclidean space in the Coleman-de Luccia formalism. The exponential suppression is determined by the Euclidean action computed on a trajectory with definite boundary conditions, known as Coleman-de Luccia instanton, or bounce. In some theories, the bounce may not exist or its on-shell action may be ill-defined or infinite, thus hindering the vacuum decay process. The issue of vacuum stability is, in fact, not just speculation: the Standard Model vacuum state is itself metastable. The Higgs field may tunnel outside its potential well, with catastrophic consequences for all observers. Luckily, the typical lifetime of such a state is predicted to be very long. Still, unknown high energy physics can change it by several orders of magnitude, and particle physics theories as well as cosmological models that predict large decay rates are ruled out thanks to the anthropic principle. Moreover, gravitational effects play an important role in this process, especially in the early Universe. It is thus important to examine in detail vacuum decay phenomena in gravitational settings and to keep the underlying field theory as general as possible. This thesis aims at exploring existence conditions for the Coleman-de Luccia instanton in gravitational settings. The first two chapters are dedicated to outlining the basic formalism and describing preexisting results about vacuum decay in cosmology. The Euclidean path integral approach for decay rate calculations, which was first discussed by Callan and Coleman, is introduced in Chapter 1. A quantum mechanical description of the problem is formulated and then extended to field theory. A detailed analysis of bounce calculations and their physical interpretation as bubbles of true vacuum follows. The Higgs field stability within the Standard Model is also addressed. Gravitational effects on the vacuum decay process are considered in Chapter 2, by focusing on the decay from Minkowski and de Sitter space, as they have important cosmological consequences respectively in the current Universe (due to the smallness of the cosmological constant) and at early times. The implications on Higgs decay are discussed in both settings. The last two chapters are dedicated to new results. Vacuum decay in field theories with a scalar field and quadratic gravity is investigated. An Einstein-Hilbert term, a non-minimal coupling, and a quadratic Ricci scalar are considered while keeping the scalar field potential general. The focus is on decay from Minkowski and de Sitter space, due to their importance in cosmology. Scalar fields with Einstein-Hilbert gravity are discussed in Chapter 3, by showing that the bounce at large Euclidean radii has an analytical form that is almost entirely independent of the potential, which is called the "asymptotic bounce". Bounds on the Hubble parameter in the de Sitter case are also explored, by giving an analytical explanation to numerical evidence present in the literature. These properties are used, in Chapter 4, to test for stabilization of the false vacuum state in quadratic gravity. Conclusions follow.