Investigation Of Structural And Magnetic Properties Of Iron Clusters Encapsulated In Carbon,
2011
University of Nevada, Las Vegas
Investigation Of Structural And Magnetic Properties Of Iron Clusters Encapsulated In Carbon, Andrew Mohrland, Eunja Kim, Phillipe Weck, Pang Tao, Kenneth Czerwinski
Festival of Communities: UG Symposium (Posters)
Our goal is to investigate and predict the properties of iron-carbon nanostructures by performing numerical calculations using the density-functional theory. We are interested in which nanostructures are most stable, and in how they are likely to form. We have a particular interest in the magnetic properties of carbon "buckyballs" containing iron particles. These structures have potential for biomedical application, including use in anti-cancer treatment. Lone iron clusters have potential for use as a catalyst designed to reduce vehicle emissions.
X-Ray Diffraction On The Thermoelectric Silicides At High Pressure,
2011
University of Nevada, Las Vegas
X-Ray Diffraction On The Thermoelectric Silicides At High Pressure, Deep Patel, Ravhi S. Kumar, Andrew Cornelius
Festival of Communities: UG Symposium (Posters)
Cobalt Silicide (CoSi2) is a transition metal disilicide that has gathered scientific interest due to its interesting thermoelectric properties and applications in silicon-based devices because of their high temperature stability. It has been reported that CoSi2 undergoes a phase transition at around 0.4 GPa and again at 13 GPa. Furthermore, at 13 GPa the material changes from a cubic cell to an orthorhombic cell, but details of the phase transition at 0.4 GPa could not be determined. To further study the properties of CoSi2 and understand its pressure induced phase changes, we recorded the structural behavior of CoSi2 under pressure.
Oxygen Vacancies Adjacent To Cu(2+) Ions In Tio(2) (Rutile) Crystals,
2011
West Virginia University
Oxygen Vacancies Adjacent To Cu(2+) Ions In Tio(2) (Rutile) Crystals, A. T. Brant, Shan Yang (杨山), Nancy C. Giles, Zafar Iqbal, A. Manivannan, Larry E. Halliburton
Faculty Publications
Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are used to characterize Cu2+ ions substituting for Ti4+ ions in nominally undoped TiO2 crystals having the rutile structure. Illumination at 25 K with 442 nm laser light reduces the concentration of Cu2+ ions by more than a factor of 2. The laser light also reduces the EPR signals from Fe3+ and Cr3+ ions and introduces signals from Ti3+ ions. Warming in the dark to room temperature restores the crystal to its preilluminated state. Monitoring the recovery of the photoinduced changes in the Cu …
Increased Power And Detuning Of Diode Lasers For Magneto-Optical Trap Of Lithium,
2011
Bethel University
Increased Power And Detuning Of Diode Lasers For Magneto-Optical Trap Of Lithium, Jami Johnson
Honors Student Works
Precision experiments such as laser cooling and trapping using diode laser systems are increasingly prevalent in the fields of modern atomic, molecular and optical physics. Multiple laser diodes of precise frequencies and significant output power are often needed for such research. Here, a method for injection locking a slave laser to a master laser stabilized to an atomic line of lithium is described.The slave laser is a free running diode that is injection-locked by a small portion (2 mW) of the frequency shifted master laser light. Evidence of incomplete injection locking is described, in addition to a technique for improving …
Phase Sensitive Detection: Frequency Locking Of A Laser Diode For Lithium Cooling And Trapping,
2011
Bethel University
Phase Sensitive Detection: Frequency Locking Of A Laser Diode For Lithium Cooling And Trapping, Brandon Peplinski
Honors Student Works
The frequency of a laser-diode can be locked by providing a negative feedback voltage to the piezo-electric transducer in the laser cavity. By phase-modulating the light and placing side bands on the carrier frequency, the fluorescence of the atoms is modulated. The signal from this fluorescence is phase-sensitively compared with a phase-locked reference signal in a lock-in amplifier, and an asymmetric error signal is produced. With this feedback method a laser-diode is locked within a 75 Mhz doppler-broadened spectroscopic line width. The lock is robust enough to last a few hours at a time and is impervious to high amplitude, …
Local Origins Of Volume Fraction Fluctuations In Dense Granular Materials,
2011
Gettysburg College
Local Origins Of Volume Fraction Fluctuations In Dense Granular Materials, James G. Puckett, Frederic Lechenault, Karen E. Daniels
Physics and Astronomy Faculty Publications
Fluctuations of the local volume fraction within granular materials have previously been observed to decrease as the system approaches jamming.We experimentally examine the role of boundary conditions and interparticle friction μ on this relationship for a dense granular material of bidisperse particles driven under either constant volume or constant pressure.Using a radicalVorono¨ı tessellation, we find the variance of the local volume fraction φ monotonically decreases as the system becomes more dense, independent of boundary condition and μ. We examine the universality and origins of this trend using experiments and the recent granocentric model, modified to draw particle locations from an …
Electromagnetic Wave Propagation In Two-Dimensional Photonic Crystals,
2011
CUNY New York City College of Technology
Electromagnetic Wave Propagation In Two-Dimensional Photonic Crystals, Oleg L. Berman, Vladimir S. Boyko, Roman Ya. Kezerashvili, Yurii E. Lozovik
Publications and Research
No abstract provided.
Cathodoluminescence Of Irradiated Hafnium Dioxide,
2011
Air Force Institute of Technology
Cathodoluminescence Of Irradiated Hafnium Dioxide, Emily A. Purcell
Theses and Dissertations
The purpose of this research is to understand the effect of radiation on HfO2 thin films, and to compare the quality of HfO2 thin films produced by both atomic layer deposition (ALD) and pulsed laser deposition (PLD); PLD samples had varying substrate temperatures during deposition (300°C, 500°C, and 750°C). The entirety of this research was conducted using cathodoluminescence (CL) as the examination method. The excitation source was a Kimball Physics EMG-12 electron gun. The photomultiplier tube contained a gallium arsenide photocathode. Measurements were made with beam energies ranging from 1 to 10 keV and beam currents ranging from …
Improving The Efficiency Of Photon Collection By Compton Rescue,
2011
Air Force Institute of Technology
Improving The Efficiency Of Photon Collection By Compton Rescue, Alexander W. Stevenson
Theses and Dissertations
A method to improve the efficiency of photon collection in thin planar HPGe detectors was investigated. The method involved implementing a second HPGe detector to collect Compton scattered photons from the primary detector and incorporating coincident interactions in the two detectors that sum to the full energy event into the energy spectrum. This method is termed Compton rescue because the Compton scattered photons make a partial energy deposition in the primary detector and are added back to the spectrum after being detected by the second detector. This research has implications on improving the efficiency of positron annihilation spectroscopy (PAS) techniques …
Structures And Photoelectron Spectroscopy Of Cun(Bo2)M− (N, M = 1, 2) Clusters: Observation Of Hyperhalogen Behavior,
2011
State Key Laboratory of Molecular Reaction Dynamics, Chinese Academy of Sciences
Structures And Photoelectron Spectroscopy Of Cun(Bo2)M− (N, M = 1, 2) Clusters: Observation Of Hyperhalogen Behavior, Yuan Feng, Hong-Guang Xu, Weijun Zheng, Hongmin Zhao, Anil K. Kandalam, Puru Jena
Physics & Engineering Faculty Publications
No abstract provided.
Superlattice Ultrasonic Generation,
2011
Marshall University
Superlattice Ultrasonic Generation, Thomas E. Wilson, M. Oehme, E. Kasper, H-J. L. Gossmann
Physics Faculty Research
We report the first experimental evidence for the resonant excitation of coherent high-frequency acoustic phonons in semiconducting doping superstructures by far-infrared laser radiation. After a grating-coupled delta-doped silicon doping superlattice is illuminated with ~1 kW/mm2 nanosecond-pulsed 246 GHz laser radiation, a delayed nanosecond pulse is detected by a superconducting bolometer at a time corresponding to the appropriate time-of-flight for ballistic longitudinal acoustic phonons across the (100) silicon substrate. The absorbed phonon power density in the microbolometer is observed to be ~10 μW/mm2, in agreement with theory. The phonon pulse duration also matches the laser pulse duration. The …
Shock Wave Dynamics Of Novel Aluminized Detonations And Empirical Model For Temperature Evolution From Post-Detonation Combustion Fireballs,
2011
Air Force Institute of Technology
Shock Wave Dynamics Of Novel Aluminized Detonations And Empirical Model For Temperature Evolution From Post-Detonation Combustion Fireballs, Joe Motos Gordon
Theses and Dissertations
This research characterizes the blast wave and temperature evolution of an explosion fireball in order to improve the classification of aluminized conventional munitions based on a single explosive type such as RDX. A drag model fit to data shows initial shock velocities of 1.6-2.8 km/s and maximum fireball radii ranging from 4.3-5.8 m with most of the radii reached by 50 ms upon detonation. The Sedov-Taylor point blast model is fitted to data where a constant release (s=1) of energy upon detonation suggests shock energies of 0.5-8.9 MJ with blast dimensionalities indicative of the spherical geometry (n3) observed in visible …
Remote Quantification Of Smokestack Total Effluent Mass Flow Rates Using Imaging Fourier-Transform Spectroscopy,
2011
Air Force Institute of Technology
Remote Quantification Of Smokestack Total Effluent Mass Flow Rates Using Imaging Fourier-Transform Spectroscopy, Jacob L. Harley
Theses and Dissertations
A Telops Hyper-Cam midwave infrared (1.5 − 5.5μm) imaging Fourier-transform spectrometer (IFTS) was used to estimate industrial smokestack total effluent mass flow rates by combining spectrally-determined species concentrations with flow rates estimated via analysis of sequential images in the raw interferogram cube. Strong emissions from H2O, CO2, CO, SO2, and NO were observed in the spectrum. A previously established plume radiative transfer model was used to estimate gas concentrations, and a simple temporal cross-correlation analysis of sequential imagery enabled an estimation of the flow velocity. Final effluent mass flow rates for CO2 and …
Understanding The Influence Of Turbulence In Imaging Fourier-Transform Spectrometry Of Smokestack Plumes,
2011
Air Force Institute of Technology
Understanding The Influence Of Turbulence In Imaging Fourier-Transform Spectrometry Of Smokestack Plumes, Jennifer L. Massman
Theses and Dissertations
An imaging Fourier-transform spectrometer (IFTS) was used to collect infrared hyper-spectral imagery of smokestack plume of a coal-burning power facility to assess the influence of turbulence on spectral retrieval of temperature (T) and pollutant concentrations (Ci). Radiance fluctuations due to plume turbulence introduced scene change artifacts (SCA) in the spectra. Time-averaging the spectra minimizes SCA magnitudes, but accurate T and Ci retrieval would require a priori knowledge of the statistical distribution of temperature and other stochastic flow field parameters. A method of quantile sorting in interferogram space that would allow the retrieval of the temperature distribution is …
Passive Ranging Of Dynamic Rocket Plumes Using Infrared And Visible Oxygen Attenuation,
2011
Air Force Institute of Technology
Passive Ranging Of Dynamic Rocket Plumes Using Infrared And Visible Oxygen Attenuation, Robert Anthony Vincent
Theses and Dissertations
Atmospheric oxygen absorption bands in observed spectra of boost phase missiles can be used to accurately estimate range from sensor to target. This work compares two oxygen absorption bands in the near-infrared (NIR) and visible (Vis) spectrum, centered at 762nm and 690 nm, to passively determine range. Spectra were observed from static tests of both surface-to-air missile simulators at 405m range and a full-scale solid rocket motor at 900m range. The NIR O2 band provided range estimates accurate to within 3% for both tests, while the Vis O2 band had range errors of 77% and 15 %, respectively. …
Evidence For The Generation Of Coherent Longitudinal Acoustic Phonons Through The Resonant Absorption Of Pulsed Far-Infrared Laser Radiation In Silicon Doping Superlattices,
2011
Marshall University
Evidence For The Generation Of Coherent Longitudinal Acoustic Phonons Through The Resonant Absorption Of Pulsed Far-Infrared Laser Radiation In Silicon Doping Superlattices, Thomas E. Wilson
Physics Faculty Research
We report the first experimental evidence for the direct excitation of coherent high-frequency acoustic phonons in semiconducting doping superstructures by electromagnetic fields of the same frequency. Nanosecond pulses of acoustic phonons have been detected by a superconducting bolometer at the appropriate time-of-flight across a (100) silicon substrate for ballistic longitudinal phonons when a silicon doping superlattice is illuminated with grating-coupled nanosecond-pulsed 246-GHz laser radiation with power density of ∼1 kW/mm2. The absorbed phonon power density in the microbolometer is estimated to be ∼ 10/Wmm2, in agreement with theory. The phonon pulse duration matches the laser pulse …
Raman Scattering Analysis Of Silicon Dioxide Single Crystal Treated By Direct Current Plasma Discharge,
2011
Faculty of Physics, University of Belgrade, Serbia
Raman Scattering Analysis Of Silicon Dioxide Single Crystal Treated By Direct Current Plasma Discharge, Dusan M. Poparic, Vladimir Milosavljevic, Andrijana Zekic, N Romcevic, Steven Daniels
Articles
Low-k materials such as silicon dioxide (SiO2) play an important role in the semiconductor industry. Plasma has become indispensable for advanced materials processing. In this work a treatment of SiO2single crystal by direct current plasma discharge is studied in detail. Offline metrology is conducted for silicon dioxide wafers by Raman scattering, energy-dispersive x-ray spectroscopy, and ellipsometry. Broad Raman peak at around 2800 cm−1 is observed for the treatedSiO2 wafers. Effects of plasma treatment on position of this peak are reported in the paper. An analysis of this correlation could be a framework for creating virtual etch rate sensors, which might …
Oscillator Strength Measurements In Singly-Ionized, Doubly-Ionized And Neutral Lanthanides And Transition Elements (Sm, Nd, Pr, Gd, Cu, And Fe) Using Laser-Induced Breakdown Spectroscopy.,
2011
Wayne State University
Oscillator Strength Measurements In Singly-Ionized, Doubly-Ionized And Neutral Lanthanides And Transition Elements (Sm, Nd, Pr, Gd, Cu, And Fe) Using Laser-Induced Breakdown Spectroscopy., Caleb Ryder
Wayne State University Dissertations
Models for stellar nucleosynthesis, age determinations for stars in the Milky Way's galactic halo, and stellar chemical abundance determinations are dependent upon accurate atomic spectroscopic data to allow the correct interpretation of stellar absorption and emission spectra. It is well known that calculations of many astrophysically important atomic parameters are limited due to line blending, insufficient spectral resolution of some key spectral lines, and also the complicated electronic structure of the important heavy elements. Astrophysicists have therefore looked to laboratory astrophysics experiments to provide accurate atomic data to help resolve these limiting issues. In this dissertation, laser-induced breakdown spectroscopy (LIBS) …
Schottky Barrier Formation At The Au To Rare Earth Doped
Gan Thin Film Interface,
2011
Air Force Institute of Technology
Schottky Barrier Formation At The Au To Rare Earth Doped Gan Thin Film Interface, S. R. Mchale, J. W. Mcclory, J. C. Petrosky, J. Wu, R. Palai, Yaroslav B. Losovyj, Peter A. Dowben
Peter Dowben Publications
The Schottky barriers formed at the interface between gold and various rare earth doped GaN thin films (RE = Yb, Er, Gd) were investigated in situ using synchrotron photoemission spectroscopy. The resultant Schottky barrier heights were measured as 1.68 ± 0.1 eV (Yb:GaN), 1.64 ± 0.1 eV (Er:GaN), and 1.33 ± 0.1 eV (Gd:GaN). We find compelling evidence that thin layers of gold do not wet and uniformly cover the GaN surface, even with rare earth doping of the GaN. Furthermore, the trend of the Schottky barrier heights follows the trend of the rare earth metal work function.
Mesoscale Flux-Closure Domain Formation In Single-Crystal Batio3,
2011
Queen’s University Belfast
Mesoscale Flux-Closure Domain Formation In Single-Crystal Batio3, R. G.P. Mcquaid, L. J. Mcgilly, Pankaj Sharma, Alexei Gruverman, J. M. Gregg
Alexei Gruverman Publications
Over 60 years ago, Charles Kittel predicted that quadrant domains should spontaneously form in small ferromagnetic platelets. He expected that the direction of magnetization within each quadrant should lie parallel to the platelet surface, minimizing demagnetizing fields, and that magnetic moments should be configured into an overall closed loop, or flux-closure arrangement. Although now a ubiquitous observation in ferromagnets, obvious flux-closure patterns have been somewhat elusive in ferroelectric materials. This is despite the analogous behaviour between these two ferroic subgroups and the recent prediction of dipole closure states by atomistic simulations research. Here we show Piezoresponse Force Microscopy images of …
