Atomic, Molecular and Optical Physics Commons^™

Photoassociative Spectroscopy Of Ultracold Metastable Argon, M. K. Shaffer, G. Ranjit, C. I. Sukenik, M. Walhout

University Faculty Publications and Creative Works

We present results of photoassociative spectroscopy performed on ultracold metastable argon atoms in a magneto-optical trap. Ion spectra are obtained with laser detuning up to a few gigahertz below the 4s[3/2]2→4p[5/2] 3 trapping transition at 811 nm and with intensities in a range of ∼(102-105)ISat. We also compute dipole-dipole potentials for both singly and doubly excited diatomic molecules and use a Leroy-Bernstein analysis to determine the approximate vibrational spacings in the (s+p) and (p+p) manifolds. Based on this theoretical framework, we explain a broad background feature in our data and suggest that double-excitation mechanisms are likely responsible for sharp dips …

Next-To-Next-To-Leading-Order Collinear And Soft Gluon Corrections For T-Channel Single Top Quark Production, Nikolaos Kidonakis

Faculty Articles

I present the resummation of collinear and soft-gluon corrections to single top quark production in the t channel at next-to-next-to-leading logarithm accuracy using two-loop soft anomalous dimensions. The expansion of the resummed cross section yields approximate next-to-next-to-leading-order cross sections. Numerical results for t-channel single top quark (or single antitop) production at the Tevatron and the LHC are presented, including the dependence of the cross sections on the top quark mass and the uncertainties from scale variation and parton distributions. Combined results for all single top quark production channels are also given.

Electron-Positron Pair Creation Induced By Quantum-Mechanical Tunneling, M Jiang, W Su, X Lu, Z M. Sheng, Y T. Li, J Zhang, Rainer Grobe, Qichang Su

Faculty publications – Physics

We study the creation of electron-positron pairs from the vacuum induced by two spatially displaced static electric fields. The strength and spatial width of each localized field is less than required for pair creation. If, however, the separation between the fields is less than the quantum-mechanical tunneling length associated with the corresponding quantum scattering system, the system produces a steady flux of electron-positron pairs. We compute the time dependence of the pair-creation probability by solving the Dirac equation numerically for various external field sequences. For the special case of two very narrow fields we provide an analytical expression for the …

A Biosynthetic Membrane-Anchor/Protein System Based On A Genetically Encoded "Aldehyde Tag", Chaojie Zhen

Renée Crown University Honors Thesis Projects - All

Lipid membranes or bilayers serve as barriers for the cell and its organelles. A distinguishing feature of cellular function is the ability to monitor and process the biochemical information between the cells’ intra and extracellular environments in order to maintain the homeostatic reactions that are essential to life. Surface membrane proteins play a key role in mediating this information exchange by functionalizing the bilayer. As a result of their importance in living systems, proteins are integrated into biomimetic membrane systems to replicate their natural functions in biomedical technologies. Current protein integration methods are limited by the selection of commercially available …

Dispersion Of The Hyperpolarizability Of The Carbon Tetrachloride Molecule, Scott Wilde

UNLV Theses, Dissertations, Professional Papers, and Capstones

The second hyperpolarizability of a molecule is the microscopic version of the third order susceptibility. Direct measurements of the ratio of the second hyperpolarizability of carbon tetrachloride to diatomic nitrogen are made possible through electric field induced second harmonic generation. Whenever the dispersion of the second hyperpolarizability is not negligible, there should be deviations from Kleinman symmetry. Previous experimental data for second hyperpolarizability of this molecule have only been at two frequencies and theory predicts the zero frequency value. In order to provide for a better extrapolation to zero frequency, additional gas phase measurements of this ratio at optical frequencies …

Symmetry-Based Techniques For Qualitative Understanding Of Rovibrational Effects In Spherical-Top Molecular Spectra And Dynamics, Justin Chadwick Mitchell

Graduate Theses and Dissertations

Using light to probe the structure of matter is as natural as opening our eyes. Modern physics and chemistry have turned this art into a rich science, measuring the delicate interactions possible at the molecular level.

Perhaps the most commonly used tool in computational spectroscopy is that of matrix diagonalization. While this is invaluable for calculating everything from molecular structure and energy levels to dipole moments and dynamics, the process of numerical diagonalization is an opaque one. This work applies symmetry and semi-classical techniques to elucidate numerical spectral analysis for high-symmetry molecules.

Semi-classical techniques, such as the Potential Energy Surfaces, …

The Economics Of The Atomic Bomb: Cost And Utilization, Jonathan M. Davis Mr.

Senior Honors Theses

Few moments in human history can be compared to the culmination of events that brought the atomic bomb into creation.  It is incredible to contemplate that while a nation was fighting a two front war that spanned from Europe into the Pacific, that the United States was able to utilize the time, energy, brains, materials, manpower, and capital to complete a project in four years. That under any other circumstances would have taken greater than half a century to complete.

First, this thesis will discuss breakthroughs in research that led scientists to believe that the atomic weapons could be built, …

Structure Studies On Lanthanide Technetium Pyrochlores As Prospective Host Phases To Immobilize 99- Technetium And Fission Lanthanides From Effluents Of Reprocessed Used Nuclear Fuels, Thomas Hartmann, Ariana Alaniz

Festival of Communities: UG Symposium (Posters)

We performed a systematic investigation of the incorporation of 99Tc into pyrochlore oxide structures, Ln2Tc2O7, where Ln represents trivalent lanthanide Ln3+ cations, while 99Tc is atetravalent, Tc4+, metal cation. Pyrochlore compounds are high-melting temperature oxides and are recognized for their durability. Our goal in this preliminary study is to characterize and quantify the range of stability of the lanthanum technetium pyrochlore oxide phase. Hereby, powder X-ray diffraction (XRD) and Rietveld analysis were used to determine and characterize the crystalline phase content with high accuracy, and scanning electron microscopy (SEM) was used to characterize the microstructure and homogeneity of the synthesized …

Oral Presentation: Next Generation Nuclear Fuels, Douglas Hanks

Festival of Communities: UG Symposium (Posters)

Zirconium carbide has been proposed as a coating layer for next generation (“TRISO”) nuclear fuel, and is intended as a diffusion barrier to contain fission products (e.g., Pd). To study the chemical interaction between Pd and ZrC, their interface was investigated using X-ray Photoelectron Spectroscopy (XPS). Pd was step-wise deposited onto ZrC in ultra-high vacuum, and the chemical interaction at the interface was monitored, also as a function of temperature (up to 1000 C). In the presentation, details of the chemical interaction and changes in the chemical environment of Pd and their relevance for TRISO fuel will be discussed.

Hipsec X-Ray Diffraction And Infrared Spectroscopy Studies On Energetic Materials Under Extreme Conditions, Mai Huong Bausch, Yu Liu

Festival of Communities: UG Symposium (Posters)

We conducted a series of experiments on the decompositions of the energetic materials NaBH4, NH3BH3, HMX, and RDX under different pressures using the x-ray diffraction (XRD) technique; we also studied the lesser known but high-performance explosive FOX-7’s behaviors under high pressures using the infrared spectroscopy (IR) technique. For the chemical decomposition of NaBH4 and NH3BH3 we discovered possible x-ray induced hydrogen gas generation; for the decomposition of HMX and RDX, we discovered that the decay rates of these two materials vary with pressure respectively; for the study of FOX-7’s high pressure behaviors we discovered potential phase changes and pressure induced …

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, 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, 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, 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, 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, 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, Oleg L. Berman, Vladimir S. Boyko, Roman Ya. Kezerashvili, Yurii E. Lozovik

Publications and Research

No abstract provided.

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 …

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, 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, 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, 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, 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 (C_i). 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 C_i 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, 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, 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, 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 …

In Memoriam: Robert Katz (1917–2011), M. P. R. Waligorski, Francis A. Cucinotta

Robert Katz Publications

Bob Katz will be well remembered for his enthusiasm and strong personality. In a scientific dispute, few indeed could match his wit or his sense of humor or survive the cutting logic of his arguments. To those who had appreciation for his science and his personality, he was truly a great scientist and a master teacher. There are many people around the world who will remember Bob Katz for what he offered them and for the way he showed them what truth in science is.

The Katz Model, developed at that time for solid-state detectors and for cell cultures, relates …

In Vitro Analysis Of Immersed Human Tissues By Raman Microspectroscopy, Franck Bonnier, A. Mehmood, Peter Knief, Aidan Meade, Helen Lambkin, Kathleen Flynn, V. Mcdonagh, C. Healy, T. C. Lee, Fiona Lyng, Hugh Byrne

Articles

Raman microspectroscopy is a powerful tool for the analysis of tissue sections, providing a molecular map of the investigated samples. Nevertheless, data pre-processing and, particularly, the removal of the broad background to the spectra remain problematic. Indeed, the physical origin of the background has not been satisfactorily determined. Using 785 nm as source in a confocal geometry, it is demonstrated for the example of the protein kappa-elastin that the background and resulting quality of the recorded spectrum are dependent on the morphology of the sample. Whereas a fine powder yields a dominant broad background, compressed pellets and solution-cast thin films …

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) …

Resonant Photoemission Of Rare Earth Doped Gan Thin Films, S. R. Mchale, J. W. Mcclory, J. C. Petrosky, J. Wu, R. Palai, Yaroslav B. Losovyj, Peter A. Dowben

Peter Dowben Publications

The 4d → 4f Fano resonances for various rare earth doped GaN thin films (RE = Gd, Er, Yb) were investigated using synchrotron photoemission spectroscopy. The resonant photoemission Fano profiles show that the major Gd and Er rare earth 4f weight is at about 5–6 eV below the valence band maximum, similar to the 4f weights in the valence band of many other rare earth doped semiconductors. For Yb, there is very little resonant enhancement of the valence band of Yb doped GaN, consistent with a largely 4f¹⁴ occupancy.