Classical chaotic scattering experiments were performed on ten different four hill potentials, unique under x-axis reflection, given by: V(x,y) = x²y²e⁻⁽ˣ² ⁺ ʸ²⁾ σᵢ where σᵢ was ±1 depending upon quadrant. Our work was based on a paper (9) that only studied the case where σᵢ =1 in all quadrants....
Contamination events at Oak Creek, which runs through Oregon State University Research lands, prompted investigations into alternate transport mechanisms for moving liquid effluent from OSU Diary lands to Oak Creek. Magnetometer surveys conducted at the Diary identified magnetic signatures spatially associated with sub-surface locations of drain tiles, a 12-inch pipe,...
Using ¹³C cross polarization magic angle spinning nuclear magnetic resonance techniques on 5 species of dead trees from the northwest (western hemlock, Douglas fir, Sitka spruce, lodgepole pine and ponderosa pine) I tracked the lignin and cellulose content over a 22 to 36 year period in order to determine the...
Uncertainty relations provide constraints on how well the outcomes of incompatible measurements can be predicted, and as well as being fundamental to our understanding of quantum theory, they have practical applications such as for cryptography and witnessing entanglement. Here we shed new light on the entropic form of these relations,...
Cross sections for radiative capture of neutrons have been measured by the activation technique for stable isotopes of Ba with mass numbers 130, 132, 134, 136, and 138. From separate irradiations using thermal and epithermal neutrons, independent values for the thermal cross sections and effective resonance integrals have been determined....
Premise of the study: Seed cone morphology and anatomy reflect some of the most important changes in the phylogeny and evolutionary biology of conifers. Reexamination of the enigmatic Jurassic seed cone Pararaucaria patagonica reveals previously unknown systematically informative characters that demonstrate affinities with the Cheirolepidiaceae. This paper documents, for the...
Interactions of few-cycle terahertz pulses with the induced optical polarization in a quantum-well microcavity reveal that the lower and higher exciton-polariton modes together with the optically forbidden 2p-exciton state form a unique Lambda-type three-level system. Pronounced nonlinearities are observed via time-resolved strong-terahertz and weak-optical excitation spectroscopy and explained with a...
Radiative neutron capture cross sections have been measured for the stable isotopes of natural Os with mass numbers 184, 189, 190, and 192 by observing radioactive decays of the activation products following neutron irradiation of naturally occurring Os. From irradiations of Os samples separately with thermal and epithermal neutrons, independent...
The N=88 isotones lie on the onset of nuclear deformation and have a complicated nuclear structure. To better understand this region, the nuclear levels of ¹⁵⁰Sm were studied in three different β decay experiments. De-populating γ-rays were measured using the 8π spectrometer, an array of 20 Compton suppressed Ge detectors....
The thermodynamic and structural effects of highly anisotropic, short-ranged attraction are investigated for single- and four-site interaction models using Wertheim's multi-density graph theory of chemical association. Both models consist of associating hard spheres, where the saturable attraction sites are described by conical wells centered in the hard core and evaluated...
The code is developed for the calculation of the magneto-crystalline anisotropy (MAE) in thin films using a classical Heisenberg hamiltonian with a correction developed by Van Vleck. A Metropolis style Monte Carlo algorithm was used with adequate corrections to accelerate the calculation. The MAE was calculated for the case of...
The optical response of metallic structures is dominated by the dynamics of their free electron plasma. Plasmonics, the area of optics specializing in the electromagnetic behavior of heterogeneous structures with metallic inclusions, is undergoing rapid development, fueled in part by recent progress in experimental fabrication techniques and novel
theoretical approaches....
The widespread adoption of wavelength division multiplexing to increase the bandwidth of optical fiber communication systems has provided a major impetus for research on low cost, single-mode, wavelength stable tunable diode lasers for use in optical telecommunications due to the large volume of lasers required. Other applications, such as demodulation...
Globally intermittent turbulence is characterized by sudden switching from significant turbulence to weak turbulence and back on time scales ranging from seconds to tens of minutes as opposed to microscale intermittency, which is due to organization of small scale gradients by individual eddies on scales as small as the Kolmogorov...
Nuclear techniques such as perturbed angular correlation (PAC) sample the hyperfine interactions of a large number of probe atoms in specific crystallographic sites. Real crystals contain static defects producing a distribution of electric field gradients (EFGs) that add to the ideal EFG of the crystal at any given probe site....
Computer simulations invoking the Metropolis Algorithm and Monte Carlo techniques were constructed to model the behavior ofvarious systems of magnetic semiconductors. Among the systems modeled were bulk type II FCC antiferromagnets and simple cubic thin films and superlattices. Studies of bulk antiferromagnets revealed dependence of Neel Temperature on nearest neighbor...
We report on physical mechanisms behind the temperature-dependent optical absorption, photoluminescence (PL), and photoconductivity in spin-coated films of a functionalized anthradithiophene (ADT) derivative, ADT-triethylsilylethynyl (TES)-F, and its composites with C₆₀ and another ADT derivative, ADT-TIPS-CN. Measurements of absorption and PL spectra, PL lifetimes, and transient photocurrent were performed at temperatures...
The electronic structure of the oxychalcogenides LaCuOSe and BiCuOSe has been studied using O K-edge x-ray emission spectroscopy, x-ray absorption spectroscopy, and density functional theory, in order to examine the effects of the M³⁺ ion configurations. The known distortion of the BiO layers in BiCuOSe compared to the LaO layers...
One of the newer and rapidly developing approaches in quantum computing is based on "quantum walks," which are quantum processes on discrete space that evolve in either discrete or continuous time and are characterized by mixing of components at each step. The idea emerged in analogy with the classical random...
Studies of light-matter interactions in organic semiconductors and in optical tweezer trapping of nanoparticles are presented. In the research related to organic semiconductor materials, a variety of novel materials and their composites have been characterized, and physical mechanisms behind their optoelectronic properties have been established. Three novel functionalized hexacene derivatives...
High resolution images of a dim companion in a binary star system can be obtained using a Digital Micromirror Array (DMA) as an optical mask. Imaging can be problematic because the intense light from the main star can saturate the detector and leave the companion unnoticed. Placement of the DMA...
This thesis presents a measurement of the resonance integral and thermal cross section – which together represent the total neutron absorption cross section – of the naturally occurring isotopes of platinum that emit gamma radiation upon neutron absorption. The measurements were made via neutron activation analysis. Platinum samples were bombarded...
We examine a discrete-time quantum walk with two-step memory for a particle on a one-
dimensional infinite space. The walk is defined with a four-state memory space analogous to the
two-state coin space commonly used in discrete time quantum walks, and a method is presented
for calculating the time evolution...
An apparatus and method for calibrating planar laser induced fluorescence using a two-dye, two-color method was developed. A laser sheet was expanded from a 473 nm laser to excite dye solutions into higher energy states then fluoresced through spontaneous emission. The two fluorescent dyes selected for research and development were...
Presented here is a case study of the problem-solving behaviors of upper-division undergraduate physics majors. This study explores the role of visual representations in students' problem solving and provides a foundation for investigating how students' use of visualization changes in the upper-division physics major. Three independent studies were conducted on...
We report ²⁷Al and ⁶⁹,⁷¹Ga impurity and ⁶⁷Zn host species NMR experiments on
ZnO powders containing Al or Ga dopants in the range 0.03 to 3 at. %. Spectral
analysis of the ⁶⁷Zn and ⁶⁹Ga quadrupole powder patterns indicate gallium is
substitutional for zinc and the electric quadrupole coupling of...
Immersion energies for an impurity in a homogeneous electron gas with a uniform positive background charge density have been calculated numerically using density functional theory. The numerical aspects of this problem are very demanding and have not been properly discussed in previous work. The numerical problems are related to approximations...
We exhibit long-lived resonances in scattering from two-dimensional soft cage potentials comprised of three and four Gaussian peaks. Specific low-energy resonances with very narrow width are shown to correspond to classical multiple-reflection events. These states have much larger probability densities inside the cage than outside and mimic bound states in...
Angular correlations of gamma rays from excited states of ¹⁶⁶Er have been
measured following the β decays of ¹⁶⁶ Ho (Jπ =7-, t 1/2 =1200y, Q= 1854 ke V) and ¹⁶⁶Tm (Jπ = 2+, t 1/2, = 7.7h, Q=3040 keV).
Data was collected using the 8π
spectrometer, an array of...
As part of a research program to study the transitional region of N=88
isotones, ¹⁵²Tb was produced by the reaction ¹⁵¹Eu(α,3n)¹⁵²Tb in the 88" cyclotron
located at LBNL. Gamma-ray spectroscopy of the radiation emitted from excited
¹⁵²Gd following the β⁺ decay of ¹⁵²Tb has been performed using an array of...
In an effort to develop an optical-acoustical understanding of ultrasound contrast agent microbubble dynamics in a micro-environment that resembles blood vessels, this thesis presents experimental work on optical trapping and acoustical probing of ultrasound contrast agent microbubbles confined in regenerated cellulose capillaries. First, we showed by acoustical means that the...
This study aimed to investigate students' models of probability in a modern physics context. The study was divided into three phases. The first phase explored student pre-knowledge about probability before modem physics instruction. The second phase investigated student understanding of concepts related to probability such as wave-particle behavior, the uncertainty...
In this thesis, I present studies in the field of terahertz (THz) spectroscopy. These studies are divided into three areas: Development of a narrowband THz source, the study of carrier transport in metal thin films, and the exploration of coherent dynamics of quasi-particles in semiconductor nanostructures with both broadband and...
We developed a model to investigate the dielectric properties of the
BaTiO₃ − Bi(Zn₁/₂Ti₁/₂)O₃ (BT-BZT) solid solution, which is a relaxor ferroelectric and exhibits long range disorder. The model uses ab initio methods
to determine all polarization states for every atomic configuration of 2 x 2 x 2
supercells of...
This dissertation explores the engineering of carbon nanotube electronic devices using atomic force microscopy (AFM) based techniques. A possible application for such devices is an electronic interface with individual biological molecules. This single molecule biosensing application is explored both experimentally and with computational modeling.
Scanning probe microscopy techniques, such as...
This thesis will cover work that I have completed relating to the field of terahertz (THz) science. My work has consisted of generating tunable, narrowband THz pulses in a table-top optical setup and using both narrow- and broadband THz pulses to study various material systems. Broadband THz pulses were used...
Bulk properties of CuSc₁₋ₓMgₓO₂, CuSc₁₋ₓMgₓO₂₊y, BaCu₂S₂, Bai₁₋ₓKCu₂S₂, BaCu₂Se₂
and Bai₁₋ₓKₓCu₂Se₂ are investigated supporting the search for highly conductive p-type
thin films. Mg is an efficient dopant in CuScO₂ with conductivity up to l.5.10⁻² S/cm.
Oxidation of CuScO₂:Mg leads to further increase in conductivity up to 0.5 S/cm. The
amount of...
Zinc tin oxide (ZTO) films deposited by pulsed laser deposition (PLD) are
investigated as a channel layers for transparent thin-film transistors (TTFTs).
Films are deposited on glass for characterization, and transistor channel layers are
deposited onto aluminum oxide-titanium oxide/tin doped indium oxide/glass
substrates (ATO/ITO/glass) to produce TTFTs.
UV-visible spectroscopy on...
The Seebeck coefficient is examined in the high temperature limit, using an approach based on a grand partition function containing Hubbard Hamiltonian interaction terms. Although the carriers of interest occupy localized Wannier states, this work is prefaced by the case of delocalized Bloch states, which is examined using Boltzmann transport,...
We used two temporally separated femtosecond pulses to manipulate the waveforms of multi-cycle THz pulses through optical rectification in periodically-poled lithium mobate (PPLN). The relative phase of the THz pulses was controlled by the relative time delay between the optical pulses. This phase adjustability combined with the frequency tunability of...
Crystals of CdF₂:In and CdF₂:Ga reduced in a cadmium vapor exhibit unusual
metastable properties that can be explained by a "negative U" model. This work
uses NMR to investigate this model for CdF₂:Ga and CdF₂:Ga,Y and compare the
results to optical measurements. Temperature dependent relaxation measurements
were done on ¹¹³Cd...
As electronics reach nanometer size scales, new avenues of integrating biology and electronics become available. For example, nanoscale field-effect transistors have been integrated with single neurons to detect neural activity. Researchers have also used nanoscale materials to build electronic ears and noses. Another exciting development is the use of nanoscale...
A method for bandgap energy determination using di use re ection is presented and compared to the traditional integrating sphere method. We have found the bandgap energies of ZnO, TiO₂, Cu₂O, Si, SnZrS₃, SnZrSe₃, Sn₂S₃, and BiCuOSe powders with both methods and found they agree within 0.03 eV. We have...
An investigation was made to determine teacher facilitation techniques in large lecture physics classrooms that foster small group discussion. Video recordings of an introductory calculus-based physics class were taken for the 2008-2009 academic year at Oregon State University. These videos were analyzed to determine student participation in small group discussion...
Semiconducting materials which can be ambipolarly doped are highly desirable in many electronics applications, including use as solar cell materials. SnZrS₃ is being investigated for the possibility of ambipolar doping, with potential applications as a solar cell absorber layer. This dissertation covers the synthesis of SnZrS₃ and the related compound...
Nonlinear optical processes can be described as multiphoton scattering events in terms of high order perturbation theory. The standard procedure for quantitative calculation of high order terms is to impose a steady state condition on the perturbative radiation fields. In the present work, this condition will be lifted, and explicit...
This dissertation concerns several problems in the fields of light interaction with nanostructured media, metamaterials, and plasmonics. We present a technique capable of extending operational bandwidth of hyperbolic metamaterials based on interleaved highly-doped InGaAs and undoped AlInAs multilayer stacks. The experimental results confirm theoretical predictions, exhibiting broadband negative refraction response...