Physics Commons^™

Synthesis And Characterization Of Ion-Implanted Gold Nanoparticles, Nurlathifah Fnu

Masters Theses

Gold negative ions of 70 keV energy were implanted within the quartz substrates at room temperature at seven different fluences starting from 2 x 10¹⁶ particles/cm² to 8 x 10¹⁶ particles/cm² with the increment of 1 x 10¹⁶. Prior to the implantation, Stopping and Range of Ions in Matter (SRIM) calculations were carried to obtain the Bragg peak below the surface of quartz. Rutherford Backscattering Spectrometry (RBS) was carried out using 2.0 MeV He⁺⁺ ions to measure depth and implanted fluence of gold, and learn how they varied with fluence. Backscattered He particles …

Electron Capture By Multiply Charged Ions From Molecular Targets, Justin Harris

Masters Theses

State-selective differential cross sections for single-electron capture processes in collisions of Ne^q+ (q=2, 3, 5) ions with H₂O and CO₂ have been studied experimentally at laboratory collisions energies between 45 and 250 eV, and at scattering angles between 0^o and 7:20^o by means of translational energy-gain spectroscopy technique. The translational energy spectra show that only a few final states are populated depending on the projectile's charge state, laboratory scattering angle, and the collision energy. In addition, these measurements show that the dominant reaction channels are due to non-dissociative electron capture into excited states of …

Forbidden Fe Ii Emission Line Fluxes From The Weigelt Knots Of Eta Carinae, S. Towers

Masters Theses

Eta Carinae is an unparalleled object crossing many divisions of astrophysics. It has multiple, complicated and dynamic processes leading to absorption and emission spectra across all wavelengths from radio to hard x-ray. The spectra differ spatially across Eta Carinae's extended envelope and are changing rapidly over time.

The Weigelt Knots of Eta Carinae's ejecta emit spectra of numerous forbidden iron species lines, rare on Earth, but prevalent in the unique conditions surrounding this star. The Weigelt Knots' unique conditions occur almost nowhere else, making Eta Carinae, useful not only for understanding massive stars similar to it, but for understanding the …

Theoretical Modeling Of Near-Threshold Shape Resonance Behaviour In Photodetachment Experiments, Laurentiu Dan Dumitriu

Masters Theses

This thesis attempts to better understand the results obtained from photodetachment experiments of Fe-, made by the Western Michigan University experimental atomic physics group at the Advanced Light Source (ALS), Lawrence Berkeley National laboratory.

After a relevant description of the quantum mechanics and theoretical atomic physics concepts and formulas involved in this subject, a physically realistic model, based on the square well potential, is developed. Based on this model, the theoretical photodetachment cross section is computed in order to reproduce the qualitative behavior of the experimental photodetachment cross section measured at ALS.

This development, involving programming in Fortran and numerical …

Physics Faculty Use Of Example Solutions In Teaching Introductory Physics, William O. Mamudi

Masters Theses

This study investigates how physics faculty perceive and use features of example problem solutions. Thirty physics instructors from diverse institutions participated in semi-structured interviews. In addition to open-ended questions, three example problem solution artifacts were used to focus on specific solution features. Data were analyzed to identify instructors’ goals for the use of example solutions and whether their goals were consistent with the solution features that they valued and used. The study concludes that many faculty have three major goals: keeping students cognitively involved, helping students become better problem solvers, and supporting students in learning physics. The study also found …

The Dissemination And Effective Use Of Physics Education Research In Undergraduate Instruction, Trevor Stefanick

Masters Theses

Based on the results of a national survey of physics faculty, a set of interviews was conducted of 70 physics faculty from a diverse set of institutions. The interviews included questions about the dissemination and effective use of curricula and instructional strategies based on Physics Education Research (PER), focused to obtain recommendations to the PER community that might help to spread the use of these PER-based materials. Approximately half of the interviews (those with faculty who indicated knowledge about or use of Peer Instruction) have been previously analyzed. This project is the analysis of the 38 interviews that were conducted …

The Variation Of Hydrogen Concentration In Ni/Mgh Thin Film With Temperature, Rex Nyadaufe Taibu

Masters Theses

The thermal stability of Ni/MgH thin film deposited on Si substrate by Unbalanced Magnetron Physical Vapor Deposition has been investigated using Ion Beam analysis (DBA) techniques. Rutherford Backscattering Spectrometry (RBS) and Non-Rutherford Backscattering Spectrometry (NRBS) have been used to find the composition of Magnesium, Nickel and Oxygen. Elastic Recoil Detection Analysis (ERDA) has been used to determine the concentration of hydrogen at each level of heating. Heating was done in the Ultra High Vacuum (UHV) environment using a non gassy button heater. Ni/MgH sample had lost most of its hydrogen after being heated to a temperature of about 125°C in …

The Physics Of Electron Degenerate Matter In White Dwarf Stars, Subramanian Vilayur Ganapathy

Masters Theses

White dwarfs are the remnant cores of medium and low mass stars with initial mass less than 8 times the mass of our sun. As the aging giant star expels its surface layers as planetary nebulae, the core is exposed as a white dwarf progenitor. The density of matter in white dwarfs is so high that thermal or radiation pressure no longer supports the star against the relentless pull of gravity. The white dwarf is supported by a new kind of pressure known as the degeneracy pressure, which is forced on the electrons by the laws of quantum mechanics. The …

The Effect Of A Skyrme Interaction On Nucleon Induced Reactions, Yingfa Zhang

Masters Theses

The main goal of this Master thesis is the theoretical study of the interaction between a nucleon and a nucleus. This is a fundamental method to study the structure and dynamics of nuclear systems. This thesis concentrates on the study of nucleon scattering on light nuclei, ⁶Li, ⁷Li and ¹⁴N, with the effective interaction M3Y and its modification by adding a Skyrme force. This is the first time the Skyrme interaction has been employed in scattering calculations. From a comparison of the measured differential cross section σ (θ) and the analyzing power Ay (θ) for ⁶Li …

Resonant And Non-Resonant Inelastic X-Ray Scattering Of Copper Phthalocyanine, Michelle Deleene Tuel-Benckendorf

Masters Theses

With the ever-changing demands of technology and the desire to use new materials to replace the old, researchers have the job to not only find alternative materials, but also understand their properties. There continues to be extensive research in the properties of organic semiconductors, for use in many microelectronic applications. There is very little known about the excitation properties of these materials. For my research, I have chosen to study the electronic excitations of copper phthalocyanine (CuPc), one specific organic semiconductor. To do this, we used resonant and non-resonant inelastic x-ray scattering to measure the evolution of excitations as a …

Electrical Conductivity Measurements Of Lithium-Ammonia Solutions, Mariana Constantin Barbu

Masters Theses

The topic covered in this thesis is the study of electronic interactions for liquid metal-ammonia solutions, lithium-ammonia solutions in particular. To obtain a theoretical understanding of so-called correlated electron systems.

The work focuses on sample creation and measurement of electrical conductivity of lithium-ammonia solutions varying with temperature for different concentrations. We have taken measurements in liquid lithium-ammonia mixtures using four-wire method to minimize the contact resistance. We have shown how it is possible to carry out accurate measurements of the electrical conductivity in these systems with the four wire measurements.

Optical Solitons In A Three-State Medium, Talal Ghannam

Masters Theses

When a beam of light propagates within a typical medium, absorption is a common phenomenon. This happens when the frequency of the light is close to a resonant frequency of the atoms composing the medium. But in the past few decades, it has been shown that in certain circumstances, carefully chosen pulse shapes are able to propagate without significant absorption even when the frequency of the light is close to an atomic resonant frequency. It was called Self Induced Transparency (SIT).

This phenomenon was intensively studied in the two-state systems. On the other hand, the three-state systems seems not to …

Control And Data Acquisition For An Electron Spectrometer System, Stanislav Rumega

Masters Theses

An electron spectrometer system, installed on one of the beam lines in the WMU Van de Graaff accelerator laboratory, consists of two 45^o parallel-plate electrostatic analyzers, a decelerating grid, and a channeltron. It allows the energy analysis, angular analysis, and the detection of continuum electrons ejected following the bombardment of a target with accelerated ions or electrons. First, the principles of operation of the spectrometer itself are discussed with emphasis on the energy analysis. Next, the electronics and computer interfacing required for control of the spectrometer functions and for acquisition of data are described. Finally, the control and data …

A Large Scintillation Detector For Nuclear Physics Experiments At Indiana University Cyclotron Facility, Apurva Pathak

Masters Theses

A new, large, scintillation detector, called the "K" detector has been designed and built for use in a series of nuclear physics experiments being performed at the Indiana University Cyclotron Facility (IUCF). This project describes the design, construction and testing of this scintillation detector. The K detector was designed to augment an existing detector stack at IUCF, and will serve to increase the energy range of previous studies of neutral pion production in proton-proton collisions near threshold. The test data for the current project came from a proton-proton scattering experiment, during which several runs were carried out between the bombarding …

L-Shell Resonant Electron Transfer And Excitation In Cu18-19+ + H2 Collisions, Jeffrey A. Wroblewski

Masters Theses

Measurements of L-shell resonant electron transfer and excitation (RTE) were conducted for 45-72 MeV Cu^18-19+ (Na-like and Ne-like, respectively) ions colliding with H₂ using the Western Michigan University EN tandem Van de Graaff accelerator. The RTE process involves an electron-electron interaction between the projectile and the target where electron capture occurs simultaneously with projectile excitation. In previous measurements involving RTE with subsequent L x-ray relaxation for Nb^q+ (q=28-31) ions, the magnitudes of the RTE cross sections were found to be nearly a factor of two smaller than theory. In the analogous electron-ion process of dielectronic recombination, measurements …

Band Structure For Acoustic Waves Propagating In A Periodic Elastic Media And Impurity Modes Arising From Slab Substitutions, Abdur Rahman

Masters Theses

In this thesis I study the band structure for acoustic waves propagating in a one-dimensional elastic array which forms a periodic elastic system in which band gaps are opened in the frequency spectrum. Specifically, I study the single impurity problem in this system. An impurity is introduced in the system by replacing one of the acoustic slabs with a new slab of different acoustic medium or by changing the thickness of impurity slab. I study the very narrow (in frequency) impurity modes in the band gaps which are localized about the impurity sites. Then I study the frequency of impurity …

An Experimental Apparatus For Studying Differential Scattering Of Multiply-Charged Ions From Neutral Targets Following Capture, John Edward Edens

Masters Theses

An experimental apparatus has been designed, enabling measurement of angular differential cross sections for single-electron capture (SEC). The design consists of a microchannel plate detector with a one-dimensional position sensitive anode. A bow-time shaped aperture was employed to convert a radially scattered distribution into an approximate linear one. An electrostatic retarding grid was used to separate SEC contributions from the reaction products. Measurements were made of the angular differential cross sections for SEC of Ar^q+ (q=4-6,8) ions scattering from He and Ar at impact energies of 600 to 3000 eV and angles between 0 and 23 mrad. The experimental …

The Photonic Band Structure Of Dielectric Systems With A Frequency Dependent Dielectric Function, Jiezhou Liu

Masters Theses

The concepts of band theory for electrons can be employed to describe the behavior of electromagnetic waves propagaiting in periodic dielectric structures with a frequency independent dielectric function. These periodic structures can produce photonic band gaps in which the propagation of electromagnetic waves is strictly prohibited. The introduction of a frequency dependent dielectric function in such systems gives rise to strong changes of the photonic bands in the neighborhood of the frequency resonance of the dielectric function.

In my thesis, the photonic band structure of a dielectric system with a frequency dependent dielectric function which undergoes a dielectric resonance will …

Determination Of The Bulk Modulus Of A Lennard-Jones Solid, Spencer A. Van Roekel

Masters Theses

The quantum Monte Carlo method is used to determine the bulk modulus of a Lennard-Jones solid. The quantum Monte Carlo method is discussed in detail and is compared with other numerical methods used previously.

The zero pressure bulk modulus of a Lennard-Jones solid is computed at a number of different temperatures and compared with experimental data.

An Experimental Apparatus For Studying Double Differential Scattering By Low-Energy Multiply Charged Ions From Atomic Targets, Meenatchi S. Gopinathan

Masters Theses

A new differential energy-gain spectrometer with a movable parallel-plate electrostatic energy analyzer has been constructed and tested for the study of double differential (in energy and angle) cross sections for state-selective electron capture processes in collisions of low-energy multiply charged ions with atomic gases. The ion beam is produced by extracting recoil ions from a primary interaction region where these ions are generated in collisions between a neutral target gas and a fast fluorine beam from the WMU tandem Van de Graaff accelerator. An einzel lens is used to focus the ion beam extracted from the recoil-ion source into a …

Absolute Photonic Band Gaps Of Zincblende, Ulrich Bass

Masters Theses

One concept of examining the propagation of an electromagnetic wave through a periodic structure is the dispersion curve which relates the frequency of the propagating wave to its wave vector. In some cases frequency ranges occur where no propagation is possible. These ranges are called absolute photonic band gaps as far as periodic dielectric structures are concerned.

In my thesis I am interested in the dispersion curve of a Zincblende type dielectric array. Zincblende is a diamond-like structure and it has been shown that diamond structures possess absolute photonic band gaps. In studying Zincblende we want to gain deeper insight …

A Procedure For G-Matrix Calculation From A Momentum Space Potential, Zhaohui Gao Busche

Masters Theses

In this work a numerical procedure was found to calculate the G-matrix in momentum space with a momentum space potential. The integral equation for the G-matrix was solved by conversion to a matrix equation. Two numerical integral methods, three-point Simpson method and Gaussian integral method, were employed in this process to determine the more efficient method.

The resulting G-matrix in momentum space was Fourier transformed into coordinate space. This was compared with the results of the G-matrix calculated from coordinate space directly as well as the results from solving the Bethe-Goldstone equation. A 2% accuracy was achieved with both the …

Laser-Rf Double Resonance Measurements Of The Hyperfine Structure Of V Ii, Gregory Michael Matous

Masters Theses

We have measured the hyperfine structure of ⁵¹V II using the technique of collinear fast-ion-beam laser spectroscopy. The output of a dye laser was applied collinearly to an accelerated 50 ke V ion beam to produce laser induced fluorescence spectra for the metastable 3d³4s and 3d⁴ configurations. The technique of laserradio- frequency double resonance, which utilizes an optical photon to deplete a hyperfine state and an rf photon to repopulate the state, was used to measure the hyperfine intervals to a high precision. These measurements of the hyperfine intervals allowed the determination of the magnetic …

Size Imperfections In One-Dimensional Periodic Optical Arrays, Yan Zhong

Masters Theses

The concepts of band theory for electrons can also be employed to describe the behavior of electromagnetic waves propagating in periodic dielectric structures. These periodic structures can produce photonic band gaps in which the propagation of electromagnetic waves is strictly prohibited. The introduction of impurities in such system gives rise to donor and acceptor gap modes in electron system and to energy gap modes in photonic system.

In my thesis, the impurity modes in one-dimensional, periodic, dielectric system will be studied. These modes are introduced in the 1-d dielectric structure by altering the thickness of one slab in an otherwise …

Enhanced Retroreflection Of Light From Rough Metal Surfaces, Sivakumar Natarajan

Masters Theses

The optical constants n and k measured by Johnson and Christy (1972) for the noble metals (gold, silver and copper) are used to analyze the relationship between the surface characteristics and the peak height and half-width of the backscattering peak which is observed in the angular distribution of the intensity of diffusely reflected light at a vacuum-metal interface in a direction antiparallel to the original incident beam. Surfaces with surface roughness of heights less than 200 A to 300 A will be considered and a recently developed perturbation treatment will be used in these studies.

The backscattering of light from …

Non-Resonant Transfer And Excitation For S^13+ Projectiles Colliding With Neutral Gas Targets, Liang Duo

Masters Theses

Non-resonant Transfer and Excitation (NTE) by 20-70 Mev S,3+ projectiles in collisions with neutral gas targets of He, Ne and Ar is investigated. For NTE, positively charged projectiles undergo excitation and electron capture in a single collision in which the capture and excitation processes are independent events. The mechanisms involved in the NTE process are electron-nucleus interactions, and the combination of projectile excitation and capture is a two-step process. In this work, NTE cross sections, along with total K x-ray production cross sections and total single-electron capture and loss cross sections, were measured as a function of projectile energy. The …

Impurity Modes In Photonic Band Structures, Yi-Fen Chang

Masters Theses

In this thesis I study a theoretical model of one-dimensional dielectric array (a layered system of dielectric slabs) which forms a periodic dielectric system in which band gaps are opened in the frequency spectrum. Specifically, we study such a one-dimensional array with linear impurities introduced in the periodic dielectric system. In these impurity structures narrow resonant modes are found in the band gaps as impurity modes and these impurity modes change with the dielectric constant. This impurity problem is similar to the donor and acceptor state problem in electronic semiconductors. The calculations presented in this thesis are based on numerically …

Construction Of A Lithium Vapor Oven For Electron Capture And Multiple Ionization Experiments, Oliver Woitke

Masters Theses

A Li vapor oven, to be used as a source of Li target atoms in electron capture and multiple ionization experiments, was designed and installed in the beamline of the Van de Graaff accelerator at Western Michigan University. The oven was tested using two different projectile beams, protons and He+. The test results indicate that Li evaporated from the oven in the form of a cloud rather than as a jet spray. For He+ colliding with Li it was found that the projectile single-electron loss yield is about three orders of magnitude larger than the single-electron capture yield, as expected …

Charge Conservation In The Incommensurate-Commensurate Transition Of Charge Density Waves, Jörg Kastrup

Masters Theses

W ith the complex continuation method, introduced by Gupta and Sutherland (1976), the grand partition function for the sine-Gordon model of charge density waves may be calculated without violation of charge conservation. Contrary to previous works by Okwamoto, Takayama and Shiba (1979) and Turkevich and Doniach (1982) the chemical potential becomes temperature dependent. By direct comparison of numerical results with those of the above mentioned authors it is shown that the incommensurate-commensurate transition does not occur in the previously predicted temperature range.

Localization Of Light In One Dimensional Randomly Disordered Dielectric Medium, K. Balaji

Masters Theses

The concept of localization of electrons in semiconductors has been known ever since the 1960's when P. W. Anderson and N. F. Mott made detail investigations on the transport properties of alloys. At the end of the last decade, however, physicist started looking for localization in other systems. Specifically, they looked at the localization of light and acoustic waves in disordered systems. Localization is a property which arises for all wavelike excitations in disordered media.

In this study we analyze the localization of light in one dimensional randomly disordered dielectric medium using computer simulation (numerical integration method) technique. The results …