VictorJuiz/thesis huggingface dataset:
Absolute intensities and pressure effects in the infrared fundamental bands of methane and its deuterated species
Keywords: Physics

The infrared fundamental bands of methane and its deuterated species have been examined in dilute mixtures with helium, at densities from ~100 to ~1000 amagat. There are a total of 24 active fundamentals for CH4, CH3D, CH2D2, CD3H, and CD4, although in some cases only groups of overlapping bands can be observed. For the thirteen separate bands or groups of hands, the density variation of the spectral profiles and the integrated intensities has been studied. The contours have been corrected for slit-width effects by an iterative procedure. There is progressive disappearance of the rotational structure with increasing density, until at the highest pressures only broad, almost featureless bands remain. For the stretching modes, the integrated intensity Ӷ decreases linearly with helium density; the relative decrease is the same for bands at ~3000 cm-l and ~2200 cm-l, and equal to 1.53 x 10~4 / amagat. For the deformation modes, the initial decrease in Ӷat low densities is followed by a region of constant or slightly increasing intensity…
Generating, controlling and time-resolving ultrafast photocurrents in gallium arsenide
Keywords: Physics

Three different types of ultrafast photocurrents (rectification, shift, and injection) are observed in GaAs at 300 K and temporal information is obtained using the associated emitted THz radiation. Using a simple description of the current evolution and a Green function formalism for THz propagation calculations, the current dynamics is studied via the temporal profile of the emitted THz…
Paleomagnetic results from two hydrothermally altered units in the superior province
Keywords: Physics

Two problems of Precambrian palcomagnctism, namely the scarcity of well-dated palcopolcs for this geological era, and the aggravating effects of retrograde hydrothermal alteration on the rocks from which the scanty palcomagnetic record available derives, arc evaluated by the study of two specific test-cases in the northcentral and northwestern Superior Province. The fonnations studied arc: the unaltered granitic batholiths and hydrothermally altered supracrustal units of the Archean Red Lake Grcenstone Belt (northwestern Ontario), a major gold-producing region: and the Kcwccnawan-agc carbonatites and Archean anorthositcs of the Kapuskasing Structural Zone (KSZ, northcentral Ontario), an early Proterozoic belt that has been hypothesized as a cross-section of the continental crust…
Gravity with a Twist
Keywords: Physics

A theory of gravity which describes spacetime in terms of non-Riemannian geometry is presented and studied. This Nonsymrnetric Gravity Theory (NGT) is a close relative of Einstein's general relativity, differing only fry a fundamental torsion or twist in the spacetime structure. The principal aim of the study is to investigate the existence, or otherwise, of black holes in NGT. Along the way many issues have to be addressed including the physical description of spacetime geometry and the interaction of gravity with matter. At least a partial revolution of these issue's is offered. In places results will be presented in a historical fashion, reflecting the evolution of ideas that occurred as the study progressed. The definitive result of the study is to show that there will be no Schwarzschild-type black holes in spacetimes with torsion.
Development of an infrared cavity ringdown spectroscopy experiment and measurements of water vapor continuum absorption
Keywords: Physics

The development of a quantitative infrared cavity ringdown spectroscopy experiment capable of measuring water vapor continuum absorption in the 1000 cm-1 region is described. Cavity ringdown spectroscopy (CRDS) is a new high-performance technique in which laser pulses are injected into a stable, high-finesse optical cavity called the “ringdown cavity”. Absorption coefficients are obtained from the difference in the decay time constant when an absorbing gas is added and then removed from the system. We determine the decay time constants from a nonlinear least squares analysis of individual decay events. Our CRDS experiment is designed around a 1 –m long near-confocal ringdown cavity, and is novel in that it is a gas flow experiment in which we control the relative humidity from zero to near-saturation. Most CRDS experiments to date have been in the visible region, and so we describe some of the problems associated with infrared work. There is no established theory for the water vapor continuum, and so all of our knowledge is empirically-derived. Our intercomparison of water vapor continuum measurements demonstrates that continuum absorption coefficients derived from conventional spectroscopic techniques have uncertainties > 20%. We have made water vapor continuum absorption measurements with uncertainties < 10% for selected CO2 laser transitions ranging from 931 - 969 cm-1 near 296 K. Our measurements, analyzed in terms of the continuum coefficients of self-and foreign-broadening, are found to be in good agreement with the recently-developed far wing line shape theory of Ma and Tipping. We demonstrate that empirical models of the water vapor continuum, widely used in atmospheric radiative transfer applications, significantly overestimate the self-broadened continuum and do not properly account for the foreign-broadened continuum. The performance of the infrared CRDS experiment, sources of error, and proposed improvements are all discussed.
An investigation of symmetry breaking in elementary particle physics
Keywords: Physics

The study of approximate symmetries in strong interaction physics has recently been the subject of immense theoretical interest. The group theoretical treatment of their breaking mechanisms and effects has already received exhaustive analysis. Here we go a step beyond this treatment in the hope of obtaining a clearer understanding of the underlying dynamics. This is done by considering three distinct approaches to the prob1em of calculating, within a broken symmetry scheme, the dynamical parameters of a given hadronic system.
Lattice Dynamics of Some Hexachloroplatinate Compounds As Revealed By Nuclear Quadrupole Resonance
Keywords: Physics

The nuclear quadrupole resonance (NQR) frequencies (v) of the 35cl nuclei in the compounds rubidium hexachloroplatinate (Rb2PtCRl6 ) and cesium hexachloroplatinate (Rb2PtCRl6 ) were measured as functions of temperature in the range 4-500 K, under vacuum. The corresponding spin-lattice relaxation times (T1 ) were measured at the same temperatures above 60 K in Rb2PtCRl6 and above 77 K in Rb2PtCRl6. Both v and T1 were measured as functions of hydrostatic pressure in the range 1-500 kg cm-2 at four temperatures between room temperature and 380 K. A brief description of the apparatus and techniques used is presented…
Symmetry properties and sound waves in the unconventional superconductor strontium ruthenate
Keywords: Physics

Detailed theories of the effect of the superconductivity of superconductor strontium ruthenate on the velocity and on the attenuation of sound waves are developed. Two results of particular importance come out of these studies. I show that the discontinuity in the elastic constant C66 at the superconducting transition temperature implies that the superconducting order parameter in superconductor strontium ruthenate has two components and breaks time-reversal symmetry. In addition, I show how a detailed analysis of the ultrasonic attenuation experiments performed on superconductor strontium ruthenate leads to a new model for the superconducting gap structure of superconductor strontium ruthenate. Its symmetry, and the details of the three-band norm al-state Fermi surface of superconductor strontium ruthenate, all play important roles in these studies.
Magnetic Moment of Iron - Nickel Invar Alloys Between 4 And 80 K
Keywords: Physics

The magnetic moment of several ferromagnetic f.c.c. iron—nickel alloys in the invar region has been investigated at low temperatures as a function of both the magnetic field and the temperature. A vibrating sample magnetometer has been constructed for these measurements with a relative sensitivity of three parts in 10(5). Such data resolution has permitted a detailed analysis of the temperature dependence of the measurements resulting from contributions at constant volume from spin wave and single particle excitations together with a term describing the effects of volume change on the magnetization. Because of the very large and negative thermal expansion of commercial invar (Meincke and Graham, 1963), this latter contribution is very significant. When the single particle and volume terms are considered in conjunction with other thermodynamic data, they suggest that the invar alloys can be interpreted on a rigid band model. Consequently, this model has been analyzed with the result that the static magnetoelastic anomalies can be understood on the basis of an approach to instability of the ferromagnetic state occasioned by the shape of the density of states.
An experimental investigation of the heat and mass transfer of graupel
Keywords: Physics

The heat and mass transfer of graupel growing in a simulated cloud environment has been investigated experimentally. Rigidly suspended graupel were grown in a wind tunnel airstream under liquid water contents from 0.5 to 3.0 g m-3, velocities from 1.1 to 3.0 m s-1 ambient temperatures from -4.4 to - 20.9°C, cloud droplet median volume radii from 12 to 21 μm and ambient pressures from 100 to 60 kPa. Measurements of the mass, volume, growth height, geometric shape and surface temperature with time were used to calculate the bulk collision efficiency, Nusselt and Sherwood numbers and accretion density. The Lulk collision efficiency and Nusselt number were parametrized in terms of the Stokes parameter and Reynolds number respectively. The density and cone angle were parametrized in terms of the relative graupel-air stream velocity, the cloud droplet median volume radius and the surface temperature. The surface temperature measurements were made remotely with an infrared radiometer to within ± 0.2·c, and represent the first measurements of the surface temperature of growing graupel. The bulk collision efficiency was found to be approximately 30% lower than that for ideal spheres as calculated by Langmuir and Blodgett (1946). The Nusselt number was found to be approximately 50% higher than that for smooth cones. The enhanced heat convection and mass deposition or sublimation is attributed to the roughness of the ice surface. Densities ranged between 0.16 and 0.70 g cm-3 and were between 10 and 30% bwer than those predicted by Heymsfield and Pflaum (1983) for densities lower than 0.4 g cm-3 . The parametrizations of density, cone angle, Nusselt number and bulk collision efficiency represent complete solutions to the heat and mass transfer equations for graupel. Hence the graupel stage of the cold rain process can be fully and accurately incorporated into cloud dynamical models. Such a complete numerical description has not been previously reported.
Dynamics of precipitation zones
Keywords: Physics

A simple model is formulated to represent the dynamics of freely falling zones of thermodynamically inert and non-interacting precipitation sized particles in a constant density fluid. The time dependent Navier-Stokes equations of motion and continuity equations for the air and precipitation are numerically solved for two-dimensional flow in both slab and radial symmetry. Appropriate initial-boundary conditions are specified for the system. The zones' mean vertical motion, horizontal spreading, pressure support and effects of particle size distributions are investigated. Formulae are derived for radially symmetric zones of single sized particles relating the zones' vertical convective velocity and horizontal spreading velocity to an internal Froude number. Also, a formula for the zones' momentum range is derived in terms of the internal Froude number. Onset and duration of precipitation times are studied for four different initial conditions for multi-sized particle zones and were found to vary considerably from those calculated by Kessler (1967). It was noted in one particular case that particle separation for multi-sized particle zones was as large in the horizontal direction as in the vertical direction. An example calculation for an atmosphere with an exponential density profile indicates that a mean layer density for the air and a mean layer terminal velocity for the single sized particles are reasonable assumptions to make in studies of this type.
The beta-delayed three-body breakup of neon-17 and its relation to astrophysics
Keywords: Physics

This is a study on the feasibility of using the β-delayed 3-body decay of 17Ne to constrain the astrophysically important 12C (a, 7) 160 reaction rate at stellar energies. The relative rate of this reaction to that of 3a —>12C- is believed to strongly affect the evolution of massive stars subsequent to the phase of helium burning. The usefulness of the cascade decay of 17Ne in this study hinges on the existence of a-unbound states of 160 in the decay chain. Detection of all the daughter particles, p + a + 12C in triple coincidence, is necessary to optimize the kinematic information inherent in each event to discriminate against background. The first triple-coincidence measurement was accomplished in 1996, at the TRIUMPH-TISOL facility in Vancouver, BC, Canada, in which the isobaric analogue state in 17F at 11.193 MeV (Jπ=1/2-) was observed to decay into three particles via three channels, viz., the 9.59 MeV (Jπ=1/2-) state in 160, and the 2.37 (Jπ=1/2+) and 3.50/3.55 MeV (Jπ=3/2-/5/2+) states in 13N. In two subsequent measurements, various techniques were incorporated to improve the efficiency in background discrimination. The connection between experiment and theory is made through extensive Monte Carlo simulations and analytic calculations within the framework of R -matrix theory. Based on a single-channel, 2-level R -matrix calculation, an optimum detection geometry has been defined to constrain the strength of the El component of the 12C (a, 7 ) 160 reaction. According to results from another single-channel, single-level R -matrix calculation, the 10.03 MeV state in L7F has been identified as the best candidate to constrain the strength of the E2 component. However, more studies are required before the feasibility of using the decay of 17Ne to constrain the strength of the E2 component can be established.
First measurement of the photon structure function F(2) with the ZEUS detector
Keywords: Physics

This thesis describes the methods and results of the first measurement of the proton structure function F₂ by the ZEUS collaboration. The ZEUS detector is one of two large general purpose detectors at the electron-proton colliding facility HERA located at DESY in Hamburg Germany. HERA provides collisions of 26.6 GeV electrons with 820 GeV protons, resulting in a center of mass energy an order of magnitude higher than previous fixed target electron scattering experiments. The kinematics at HERA allows the measurement of F₂ in a region o f x ana Q2 phase space previously unexplored. A total integrated luminosity of 24.7 nb-1, collected during the fall of 1992, was used for the measurement of F₂. The results reported here extend the measurement of F₂ to lower values of x by two orders of magnitude. In the parton model the behavior of F₂ at low x is highly dependent on the unknown gluon distribution and the absence of data leads to significantly different expectations of the neutral current cross sections at low x. A measurement of F₂ at low x constrains the gluon distribution. The results show a strong rise at low x.
A microscopic study of pairing and quadrupole forces in nuclei
Keywords: Physics

The competition between independent-particle and pairing correlations is studied in the quasi-spin formalism. For an infinite system, a sharp phase transition from an independent-particle state to a superconducting state is found to occur as the strength of the pairing interaction increases beyond a critical value. For finite nuclei, a smooth transition occurs. It is shown that the two situations can be understood in analytical terms. It is also shown, both numerically and analytically, that Mottelson’s pair-coupling approximation becomes exact as the number of particles becomes large. To examine the simultaneous interplay of independent-particle motion, short-range pairing correlations and long-range quadrupole-quadrupole correlations, a microscopic pair-coupled model has been developed. The new approach utilizes the coherent state representation and the fermion pair algebra in a nondegenerate multi-level model space. It leads naturally to variational equations for wave functions of the number-projected Hartree-Bogoliubov type. Excited states generated by breaking one pair are constructed on a monopole ground state. The inherent determinantal and recursive properties of this approach not only result in a simple and elegant formalism, they are also shown to make numerical computations feasible. Calculations from the model indicates a shape transition at the ground state resulting from the interplay of the short-range pairing and long-range quadrupole-quadrupole correlations. Applications of the pair-coupled model to the low-lying spectra of 116Sn have been carried out and the results discussed.
A short baseline transient electromagnetic method for use on the sea floor
Keywords: Physics

A towed electromagnetic system capable of mapping the electrical conductivity of the sea floor over a large area has many possible applications, including mapping Quaternary geology, and understanding the physical properties of midocean ridge hydrothermal systems in association with massive sulphide deposits. However, the electrical conductivity of seawater is usually much greater than that of the sea floor, rendering the majority of electromagnetic systems presently employed on land unsuitable for marine use. A theoretical study of the transient step-on responses of some common controlled source, electromagnetic systems to adjoining conductive half-spaces shows that for two systems, the horizontal, in-line, electric dipole-dipole (ERER) and horizontal, coaxial, magnetic dipole-dipole (HRHR), the position in time of the initial transient indicates the conductivity of the sea floor, while at distinctly later time, a second characteristic of the transient is a measure of the larger seawater conductivity. The diagnostic separation between the two parts of the transient response does not occur for many other systems, including several commonly used for exploration on land. The concept of apparent conductivity is defined for the transient system in terms of the time of the first arrival of the transient signal. This apparent conductivity is used to produce characteristic curves of the HRHR system response for different layered earth models. A prototype HRHR system operating on a 100 m scale has been designed and constructed. A successful test of the system in shallow water was conducted in the coastal waters of Vancouver Island. The survey yielded 37 conductivity measurements along three lines. The instruments were towed by a ship along the sea floor. The tow cable carried both current to the transmitter coil and the received signal back to the ship for processing. Both the shape and amplitude of the received signal a.re indicative of the conductivity of the bottom sediments. Inversion of the data suggest that a varying thickness of 1 2 S· m-1 mud overlies rock or sediment with a conductivity of about .1 S·m-1. Improvements in equipment design might allow the production in real time of a continuous map of the conductivity structure of the sea floor.
Structural and quantum-diffusion studies in the near-infrared-spectra of solid hydrogen
Keywords: Physics

Experimental data on the infrared spectra of the fundamental and first overtone bands of nearly pure solid orthohydrogen, of the fundamental, first, and second overtone bands of nearly pure solid parahydrogen, are applied to analyses of the energy levels of solid hydrogen and quantum diffusion. Spectra of the fundamental band of solid hydrogen with orthohydrogen concentrations in the range 75% to ~ 99% orthohydrogen were recorded at 1.05 K and ~ 5 K, i.e., above and below the order-disorder phase transition. The zero-phonon features are interpreted in terms of travelling vibrational, rotational, and orientational excitations (vibrons, rotons, and librons). The Q branches (fundamental and overtone) for ~ 100% o-H2 in the ordered state show a structured side-band, shifted by ~ 6 - 26 cm-1 from the appropriate vibrational transition frequency and due to one- and two-libron excitations; in the disordered state, this becomes a Boltzmann-modified band of half-width ~ 12 cm-1, peaked at the vibrational frequency, and due to predominantly low-energy orientational transitions of interacting o-H2 molecules. The Si(0) group of maxima in the ordered state is interpreted as the superposition of the transitions, Qi (1) + S0(O) and Qi (1) + S0 (0) + libron, where Qi (1) is an o-H2 vibron and S 0(O) is the localized rotational transition of an impurity p-H2 molecule, the J = 2 level of which is split into three sublevels by the field of the Pa3 crystal structure. Spectra of the first and second overtone bands of pure and nearly pure solid p-H2 were recorded. A number of features were observed for the first time and are interpreted in terms of the theory of Van Kranendonk. In particular, this work marks the first investigation of the second overtone region where four zero-phonon features were observed, all due to double transitions. The fundamental band of almost pure p-H2 solid was investigated for evidence of the diffusion of o-H2 impurity molecules. The absorption features in this band which are due to interacting pairs of o-H2 molecules was observed to increase as a function of time. This growth is characterized by a rate constant which has been measured as a function of temperature in the range 1.15 K to 2.10 K and concentration in the range 0.7% to 1.6% o-H2 impurity. The value and concentration dependence of the rate constant are found to be in generally good agreement with the theory of Oyarzun and Van Kranendonk. Measurements have also been made which yield the ratio of the random number of impurity pairs to the equilibrium number as a function of temperature and concentration. These data are compared with a statistical model of the diffusion process.
Baman spectra of some simple molecules in condensed phases
Keywords: Physics

Spectroscopic studies of gases at low densities allow the determination of the intramolecular properties of free molecules. To investigate intermolecular properties, the molecules must be allowed to Interact with one another. One way of causing this interaction is to compress the gases to high pressures. The progressive changes which occur in the spectrum as the density is increased can be ascribed to the action of intermolecular forces during collisions.