Atomic, Molecular and Optical Physics Commons^™

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 …

The Viability Of Aluminum Zintl Anion Moieties Within Magnesium-Aluminum Clusters, Haopeng Wang, Yeon Jae Ko, Xinxing Zhang, Gerd Gantefoer, Hansgeorg Schnoeckel, Bryan W. Eichhorn, Puru Jena, Boggavarapu Kiran, Anil K. Kandalam, Kit H. Bowen Jr.

Physics & Engineering Faculty Publications

No abstract provided.

In-Package Atmospheric Pressure Cold Plasma Treatment Of Cherry Tomatoes, N. Misra, Kevin Keener, Paula Bourke, J Mosnier, Patrick J. Cullen

Articles

Cold plasma is increasingly under research for decontamination of foods, especially fresh fruits and vegetables. The effect of cold plasma on food quality, however, remains under researched. This study investigates the effects of cold plasma generated within a sealed package from a dielectric barrier discharge on the physical quality parameters and respiration rates of cherry tomatoes. Respiration rates and weight loss were monitored continuously, while other parameters are reported at the end of storage period. Differences among weight loss, pH and firmness for control and treated cherry tomatoes were insignificant towards the end of storage life. Changes in respiration rates …

Investigation Of The Potential For Ftir As A Nondestructive Inspection Technique For Aircraft Coating Degradation, Hans G. Korth

Theses and Dissertations

Polyurethane-based aircraft coating degradation was examined using Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFTs). Two sample sets were aged in an autoclave; each containing four samples. Sample set A contained two as-cured samples and two samples treated to a level of visual degradation. Sample set B contained one sample left as-cured and three samples of differing degradation. DRIFTs spectra were collected on sample set B and singular value decomposition (SVD) was used to reveal trends between the degradation levels. Linear discriminant analysis (LDA) was then applied to the SVD coefficients to determine the most accurate spectral band for classification of …

Structural Characterization Of Atomically Thin Hexagonal Boron Nitride Via Raman Spectroscopy, James M. Bondy

Theses and Dissertations

A non-destruction evaluation of atomically thin hexagonal boron nitride (h-BN) films is critical to the U.S. Air Force and Department of Defense initiatives pursuing graphene-based electronic field effect transistors (FETs) capable of operating at terahertz frequencies. H-BN thin films an increase to the characteristic E2g 1367cm^-1 h-BN peak intensity has been correlated to an increase in film thickness. Raman spectroscopy on a h-BN film with thicknesses of 7, 14, and 21 atoms (2.5nm, 5nm, 7.5nm respectively) revealed a linear relationship between peak intensity and thickness. This relationship can mathematically be described as y=0.0265x+0.8084, and fits the data with a …

Feature Selection On Hyperspectral Data For Dismount Skin Analysis, Lindsay R. Cain

Theses and Dissertations

Many security applications require the ability to accurately identify dismounts based on their distinctive identification properties. A dismount can be identified by many personal characteristics to include clothing, height, and gait. In particular, a dismount's skin can be used as an identifying feature because of the vast variability of skin pigmentation amongst individuals. Hyperspectral data, which is comprised of hundreds of spectral channels sampled from a nearly contiguous electromagnetic spectrum, is used to detect skin spectral variability amongst dismounts. However, hyperspectral data is often highly correlated and computationally expensive to process. Feature selection methods can be employed to reduce the …

Developing A Diffraction Pattern Projection System For Neutral Atom Quantum Computation, Sanjay Khatri

Physics

No abstract provided.

An Experimental Evaluation Of Image Quality For Various Scenarios In A Chromotomographic System With A Spinning Prism, Kyle J. Dufaud

Theses and Dissertations

A lab and eld based hyperspectral chromotomographic imager has been developed at the Air Force Institute of Technology. It is a prototype used to study the requirements for a space-based system. The imager uses a high speed visible band camera behind a direct-vision prism to image both spatial dimensions and the spectral dimension at the same time. Capturing all 3 simultaneously allows for the hyperspectral imaging of transient events. The prism multiplexes the spectral and spatial information, so tomographic reconstruction algorithms must be used to separate hyperspectral channels. Experiments were conducted to compare reconstructed image quality as a function of …

Polarimetric Calibration And Characterization Of The Telops Field Portable Polarimetric-Hyperspectral Imager, Joel G. Holder

Theses and Dissertations

The Telops polarimetric-hyperspectral imager combines polarimetric and hyperspectral technologies to enable enhanced scene characterization. The Defense Threat Reduction Agency funded research at AFIT to leverage this capability to provide more accurate scene information to radiation transport models that will allow for more effective location of radiation sources within a region of interest. To support the objectives of the DTRA effort, there is a requirement for highly accurate radiometric, polarimetric, and spectral data on a pixel-by-pixel basis. The complex nature of the Telops instrument combined with working in the thermal IR waveband makes achieving this accuracy a challenge. This thesis develops …

Characterization Of Construction Material Properties Through Gamma Spectroscopy, X-Ray Fluorescence, And Hyper-Spectral Imagery For Background Correction Applications In Nuclear Detection, Jared D. Casebolt

Theses and Dissertations

Material identification through hyper-spectral imagery provides a potentially useful data input for background radiation prediction models for gamma spectrum correction in mobile nuclear detection applications. Traditional background correction methods which rely on prior information are often impractical in mobile detection. Prediction models could combine material information with spatial data to develop a suitable substitute to actual background radiation measurements. This research investigates the relationship hyper-spectral properties and natural radioactivity of construction materials. A selection of construction materials are analyzed using three instrumentation methods: 1) gamma-spectroscopy, 2) X-ray fluorescence (XRF), and 3) hyper-spectral imagery. Gamma-spectroscopy focuses on the presence of potassium …

Triplet Ground State Of The Neutral Oxygen-Vacancy Donor In Rutile Tio2, A. T. Brant, Eric M. Golden, Nancy C. Giles, Shan Yang, M. A. R. Sarker, S. Watauchi, M. Nagao, I. Tanaka, D. A. Tryk, A. Manivannan, Larry E. Halliburton

Faculty Publications

Electron paramagnetic resonance (EPR) is used to investigate the triplet (S = 1) ground state of the neutral oxygen vacancy in bulk rutile TiO₂ crystals. This shallow donor consists of an oxygen vacancy with two nearest-neighbor, exchange-coupled ³⁺ ions located along the [001] direction and equidistant from the vacancy. The spins of the two trapped electrons, one at each ³⁺ ion, align parallel to give the S = 1 state. These neutral oxygen vacancies are formed near 25 K in as-grown oxidized TiO₂ crystals by illuminating with sub-band-gap 442 nm laser light. The angular dependence of the EPR …

Neutral Nitrogen Acceptors In Zno: The 67Zn Hyperfine Interactions, Eric M. Golden, S. M. Evans, Larry E. Halliburton, Nancy C. Giles

Faculty Publications

Electron paramagnetic resonance (EPR) is used to characterize the ⁶⁷Zn hyperfine interactions associated with neutral nitrogen acceptors in zinc oxide. Data are obtained from an n-type bulk crystal grown by the seeded chemical vapor transport method. Singly ionized nitrogen acceptors (N⁻) initially present in the crystal are converted to their paramagnetic neutral charge state (N⁰) during exposure at low temperature to 442 or 633 nm laser light. The EPR signals from these N⁰ acceptors are best observed near 5 K. Nitrogen substitutes for oxygen ions and has four nearest-neighbor cations. The zinc ion …

Development Of High-Purity Optical Grade Single-Crystal Cvd Diamond For Intracavity Cooling, Andrew M. Bennett, Benjamin J. Wickham, Harpreet K. Dhillon, Ying Chen, Scott Webster, Giorgio Turri, Michael Bass

Publications

Microwave assisted chemical vapour deposited bulk diamond products have been used in a range of high power laser systems, due to low absorption across a range of wavelengths and exceptional thermal properties. However the application of polycrystalline products has frequently been limited to applications at longer wavelengths or thermal uses outside of the optical path due to the birefringence and scatter that are intrinsic properties of the polycrystalline materials. However, there are some solid state structures, including thin disc gain modules and amplifiers, that will gain significantly in terms of potential output powers if diamond could be used as a …

In-Package Nonthermal Plasma Degradation Of Pesticides On Fresh Produce, N. Misra, Shashi Pankaj, Tony Walsh, Finbarr O'Regan, Paula Bourke, Patrick J. Cullen

Articles

In-package nonthermal plasma (NTP) technology is a novel technology for the decontamination of foods and biological materials. This study presents the first report on the potential of the technology for the degradation of pesticide residues. A cocktail of pesticides, namely Azoxystrobin, Cyprodinil, Fludioxonil and Pyriproxyfen was tested on strawberries. The concentrations of these pesticides were monitored in priori and post- plasma treatment using GC-MS/MS. An applied voltage and time dependent degradation of the pesticides was observed for treatment voltages of 60, 70 and 80 kV and treatment durations ranging from 1 to 5 min, followed by 24 h in-pack storage. …

Aluminum Zintl Anion Moieties Within Sodium Aluminum Clusters, Haopeng Wang, Xinxing Zhang, Yeon Jae Ko, Andrej Grubisic, Xiang Li, Gerd Ganteför, Hansgeorg Schnöckel, Bryan W. Eichhorn, Mal-Soon Lee, Puru Jena, Anil K. Kandalam, Boggavarapu Kiran, Kit H. Bowen

Physics & Engineering Faculty Publications

No abstract provided.

A Low-Power Optical Electron Switch, Wayne Cheng-Wei Huang, Roger Bach, Peter Beierle, Herman Batelaan

Department of Physics and Astronomy: Faculty Publications

An electron beam is deflected when it passes over a silicon-nitride surface, if the surface is illuminated by a low-power continuous-wave diode laser. A deflection angle of up to 1.2 mrad is achieved for an electron beam of 29 μrad divergence. A mechanical beam-stop is used to demonstrate that the effect can act as an optical electron switch with a rise and fall time of 6 μs. Such a switch provides an alternative means to control electron beams, which may be useful in electron lithography and microscopy.

On-Chip Multi 4-Port Optical Circulators, Ramy El-Ganainy, Miguel Levy

Department of Physics Publications

We present a new geometry for on-chip optical circulators based on waveguide arrays. The optical array is engineered to mimic the Fock space representation of a noninteracting two-site Bose–Hubbard Hamiltonian. By introducing a carefully tailored magnetooptic nonreciprocity to these structures, the array operates in the perfect transfer and surface Bloch oscillation modes in the forward and backward propagation directions, respectively. We show that an array made of ð2N þ 1Þ waveguide channels can function as N 4-port optical circulators with very large isolation ratios and low forward losses. Numerical analysis using beam propagation method indicates a large bandwidth of operation.

Resonant Electron-Atom Bremsstrahlung In An Intense Laser Field, A. N. Zheltukhin, A. V. Flegel, M. V. Frolov, N. L. Manakov, Anthony F. Starace

Anthony F. Starace Publications

We analyze a resonant mechanism for spontaneous laser-assisted electron bremsstrahlung (BrS) involving the resonant transition (via either laser-assisted electron-ion recombination or electron-atom attachment) into a laser-dressed intermediate quasibound state (corresponding, respectively, to either a field-free neutral atom or a negative-ion bound state) accompanied by ionization or detachment of this state by the laser field. This mechanism leads to resonant enhancement (by orders of magnitude) of the BrS spectral density for emitted photon energies corresponding to those for laser-assisted recombination or attachment. We present an accurate parametrization of the resonant BrS amplitude in terms of the amplitudes for nonresonant BrS, for …

Wave Function For Harmonically Confined Electrons In Time-Dependent Electric And Magnetostatic Fields, Hong-Ming Zhu, Jin-Wang Chen, Xiao-Yin Pan, Viraht Sahni

Publications and Research

We derive via the interaction “representation” the many-body wave function for harmonically confined electrons in the presence of a magnetostatic field and perturbed by a spatially homogeneous time-dependent electric field—the Generalized Kohn Theorem (GKT) wave function. In the absence of the harmonic confinement – the uniform electron gas – the GKT wave function reduces to the Kohn Theorem wave function. Without the magnetostatic field, the GKTwave function is the Harmonic Potential Theorem wave function. We further prove the validity of the connection between the GKT wave function derived and the system in an accelerated frame of reference. Finally, we provide …

Characterization Of Polarized Synchrotron Light, Britny N. Delp, Jeff Corbett

STAR Program Research Presentations

The Stanford Synchrotron Radiation Light accelerates electrons around a 234-meter circumference ring at relativistic speeds. The x-ray radiation produced by this process is used in many fields of science ranging from materials science to medicine.

This project seeks to measure the polarization of the 532 nanometer wavelength component in the visible light beam emitted from the SPEAR-3 synchrotron as a function of vertical position. The beam was focused through a lens, then passed through a 532 nm band pass filter and a polarizer mounted on a rotating stand. The beam power was measured as a function of vertical position and …