Atomic, Molecular and Optical Physics Commons^™

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 …

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. …

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 …

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.

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.

Ultrafast Rempi In Benzene And The Monohalobenzenes Without The Focal Volume Effect, Timothy D. Scarborough, James Strohaber, David B. Foote, Collin J. Mcacy, Cornelis J. Uiterwaal

C.J.G.J. Uiterwaal Publications

We report on the photoionization and photofragmentation of benzene (C₆H₆) and of the monohalobenzenes C₆H₅–X (X = F, Cl, Br, I) under intense-field, single-molecule conditions. We focus 50-fs, 804-nm pulses from a Ti:sapphire laser source, and record ion mass spectra as a function of intensity in the range ~10¹³ W/cm² to ~10¹⁵ W/cm². We count ions that were created in the central, most intense part of the focal area; ions from other regions are rejected. For all targets, stable parent ions (C₆H₅X+) are …