Physics Commons^™

Optical Excitation Of Metastable Krypton And Photoassociative Spectroscopy Of Ultracold Rbar, Grady R. White

Physics Theses & Dissertations

In this presentation, we discuss results from two separate bodies of work. In the first, we investigate all-optical excitation methods to produce metastable-state krypton. The high energies required to excite rare gases out of their ground state present a unique challenge in the context of laser experiments. Laser physics work with rare gases often relies on excitation within an RF discharge. All-optical excitation is a promising replacement for RF discharges, avoids problems caused by ion production and may eventually allow for higher efficiencies. We examine three separate methods of all-optical metastable-state production: using an ArF excimer laser, using the third …

Multidimensional Spectroscopy Of Mixed-Cation Perovskite Thin Films, Geoffrey Michael Diederich

Electronic Theses and Dissertations

Metal halide perovskite (MHP) thin films are currently undergoing an intense re- search thrust due to the excellent performance of MHP based photovoltaic (PV) devices, which have the potential to revolutionize the worlds energy production via a unique combination of low-cost fabrication and high power conversion efficiency (PCE). However, the vast majority of research is currently aimed at incremental improvements in device PCE, resulting in a body of work without the foundational understanding of the charge-carrier dynamics of the system upon photoexcitation.

This thesis begins with the development of a phase-modulated multidimensional coherent spectroscopy (PM-MDCS) experiment. PM-MDCS is an ultrafast …

Studying The Interface Between Croconic Acid Thin Films And Substrates Using A Slow Positron Beam, Dean Peterson, Jiandang Liu, Jonas Etzweiler, Gabriel Sontoyo, Sara J. Callori, Kimberley R. Cousins, Timothy Usher, Renwu Zhang

Physics Faculty Publications

Croconic acid (CA) is the first organic ferroelectric with a spontaneous polarity in bulk samples comparable to its inorganic counterparts. As a natural extension of study, ultrathin CA films (∼nm scale) were investigated to reveal ferroelectric effects in films on different substrates for their fundamental and industrial significance. However, the void defect at the interface between the film and substrate is presumed to interfere with surface effects. In this work, a non-invasive technique, a slow positron beam, coupled with Doppler broadening energy spectroscopy (DBES), is applied to study the void defects within the interfacial layer between CA films and Si …

Chemical Synthesis Of Zinc Oxide Nanorods And Their Transformation Intonanotubes, Pijus Kanti Samanta

Turkish Journal of Physics

A simple wet chemical method was successfully deployed to synthesize zinc oxide nanorods and nanotubes of hexagonal morphology. Energy dispersive X-ray spectroscopy confirmed the formation of ZnO with almost equal atomic percentages of Zn and O atoms. The FESEM images confirmed the formation of ZnO nanorods and nanotubes of length 1.5 to 2 $\mu $m and diameter 500 nm to 1 $\mu $m. The growth of the nanorods saturated under the combined effect of ionic association of Zn$^{2+}$ and OH$^{-}$ ions, Gibbs' energy of the reaction, reaction temperature, and the enthalpy of the system. Further stirring led to dissolution resulting …

Spectroscopy Of Neon For The Advanced Undergraduate Laboratory, H. C. Busch, M. B. Cooper, C. I. Sukenik

Physics Faculty Publications

We describe a spectroscopy experiment, suitable for upper-division laboratory courses, that investigates saturated absorption spectroscopy and polarization spectroscopy in a neon discharge. Both experiments use nearly identical components, allowing students to explore both techniques in a single apparatus. Furthermore, because the wavelength of the laser is in the visible part of the spectrum (640 nm), the experiment is well-suited for students with limited experience in optical alignment. The labs nicely complement a course in atomic or plasma physics, provide students with the opportunity to gain important technical skills in the area of optics and lasers, and can provide an introduction …

Argon Metastable And Resonant Level Densities In Ar And Ar/Cl² Discharges Used For The Processing Of Bulk Niobium, Jeremy Peshl, Roderick Mcneill, Charles I. Sukenik, Milka Nikolić, Svetozar Popović, Leposava Vŭsković

Physics Faculty Publications

A comparative analysis of two popular spectroscopy techniques is conducted in a coaxial cylindrical capacitively coupled discharge designed for the plasma processing of superconducting radio frequency (SRF) cavities. The density of the metastable and resonant levels in Ar is measured in both Ar and Ar/Cl₂ discharges to properly characterize the unique discharge system and aid in the development of a cavity etching routine. The first method, deemed the “branching fraction method,” utilizes the sensitivity of photon reabsorption of radiative decay to measure the lower state (metastable and resonant) densities by taking ratios of spectral lines with a common upper …

Evaluation Of X-Ray Spectroscopic Techniques For Determining Temperature And Density In Plasmas, Theodore Scott Lane

Graduate Theses, Dissertations, and Problem Reports (ETD)

Temperature and density measurements of plasmas are important for understanding various phenomena. For example, equations of state, most scaling arguments for Inertial Confinement Fusion and laboratory astrophysics all rely upon accurate knowledge of temperature and density. Spectroscopy is a non-invasive technique to measure these quantities. In this work we establish a new spectroscopic technique by using it to determine temperature. We also compare and contrast the capability of two codes, PrismSPECT and ATOMIC, to infer electron density from experimentally acquired spectra via Stark broadening.

We compare and contrast the capability of isoelectronic line ratios and inter-stage line ratios in an …

Mass-Analyzed Threshold Ionization Of Lanthanide Imide Lnnh (Ln = La And Ce) Radicals From N–H Bond Activation Of Ammonia, Yuchen Zhang, Silver Nyambo, Dong-Sheng Yang

Chemistry Faculty Publications

Ln (Ln = La and Ce) atom reactions with ammonia are carried out in a pulsed laser vaporization supersonic molecular beam source. Lanthanide-containing species are observed with time-of-flight mass spectrometry, and LnNH molecules are characterized by mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical calculations. The theoretical calculations include density functional theory for both Ln species and a scalar relativity correction, electron correlation, and spin-orbit coupling for the Ce species. The MATI spectrum of LaNH exhibits a single vibronic band system with a strong origin band and two weak vibronic progressions, whereas the spectrum of CeNH displays two band systems …

Time-Resolved Double-Resonance Spectroscopy: Lifetime Measurement Of The 61Σ+G(7,31) Electronic State Of Molecular Sodium, Michael Saaranen, Dinesh Wagle, Emma Mclaughlin, Amelia Paladino, Seth Ashman, Burcin Bayram

Engineering & Physics Faculty Publications

We report on the lifetime measurement of the 61Σ+g(7,31) state of Na2 molecules, produced in a heat-pipe oven, using a time-resolved spectroscopic technique. The 61Σ+g(7,31) level was populated by two-step two-color double resonance excitation via the intermediate A1Σ+u(8,30) state. The excitation scheme was done using two synchronized pulsed dye lasers pumped by a Nd:YAG laser operating at the second harmonics. The fluorescence emitted upon decay to the final state was measured using a time-correlated photon counting technique, as a function of argon pressure. From this, the radiative lifetime was extracted by extrapolating the plot to collision-free zero pressure. We also …

Spectroscopy And Formation Of Lanthanum-Hydrocarbon Radicals Formed By C—H And C—C Bond Activation Of 1-Pentene And 2-Pentene, Wenjin Cao, Yuchen Zhang, Silver Nyambo, Dong-Sheng Yang

Chemistry Faculty Publications

La atom reactions with 1-pentene and 2-pentene are carried out in a laser-vaporization molecular beam source. The two reactions yield the same metal-hydrocarbon products from the dehydrogenation and carbon–carbon bond cleavage of the pentene molecules. The dehydrogenated species La(C₅H₈) is the major product, whereas the carbon–carbon bond cleaved species La(C₂H₂) and La(C₃H₄) are the minor ones. La(C₁₀H₁₈) is also observed and is presumably formed by La(C₅H₈) addition to a second pentene molecule. La(C₅H₈) and La(C_{2 …}

Development Of Metallic Magnetic Calorimeters And Paramagnetic Alloys Of Ag And Er For Gamma-Ray Spectroscopy, Linh N. Le

Physics & Astronomy ETDs

A Metallic Magnetic Calorimeter (MMC) is a cryogenic calorimetric particle detector that employs a metallic paramagnetic alloy as the temperature sensor material. MMCs are used in many different applications, but this work will focus on their uses in high energy resolution gamma-ray spectroscopy. This technology is of great interest to the field of Nuclear Forensics and Nuclear Safeguards as a non-destructive assay for isotopic analysis of nuclear samples. The energy resolution of MMCs is an order of magnitude higher than the benchmark High Purity Germanium (HPGe) detectors that are currently used in the field and MMCs are also poised to …

Spectroscopy And Formation Of Lanthanum-Hydrocarbon Radicals Formed By Association And Carbon-Carbon Bond Cleavage Of Isoprene, Wenjin Cao, Dilkrushi Hewage, Dong-Sheng Yang

Chemistry Faculty Publications

La atom reaction with isoprene is carried out in a laser-vaporization molecular beam source. The reaction yields an adduct as the major product and C—C cleaved and dehydrogenated species as the minor ones. La(C₅H₈), La(C₂H₂), and La(C₃H₄) are characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectra of all three species exhibit a strong origin band and several weak vibronic bands corresponding to La-ligand stretch and ligand-based bend excitations. La(C₅H₈) is a five-membered metallacycle, whereas La(C₂H_{2 …}

Precision Spectroscopy Of Beryllium, Advik D. Vira

Theses, Dissertations, and Projects

We report on the calibration and absolute frequency results for the 2s2p1P1 state in neutral atomic beryllium-9. We start off with a discussion of the method used to calibrate the laser, which includes a detailed explanation of the basic physics involved, and then discuss the results for the lowest singlet state in neutral beryllium-9. We discuss a way to predict the spectra using optical Bloch equations and then present and analyze the experimental results. We found the absolute frequency for the 1P1 state to be 42565.4487(30) cm-1, which is in agreement with the current best theoretical estimateof42565.441(11)cm-1 [49]. Amoresophisticatedanalyticaltechniqueisproposed; however, …

Excited Argon 1s5 Production In Microhollow Cathode Discharges, Richard D. Peterson

Theses and Dissertations

Diode-pumped rare gas lasers (DPRGL) have been in development for their potential to become high energy lasers with excellent beam quality that is typical of gas lasers. DPRGL require metastable densities on the order of 10¹³ cm^-3 at pressures around one atmosphere for efficient operation. Argon 1s5 number densities have been measured in microhollow cathode discharges (MHCD) using tunable diode laser absorption spectroscopy. The MHCD had copper electrodes with gaps of 127 and 254 µm and hole diameters from 100-400 µm. Absorbance was measured at pressures of 37 Torr up to 400 Torr, where absorbance could no longer …

Lanthanum-Mediated Dehydrogenation Of Butenes: Spectroscopy And Formation Of La(C4H6) Isomers, Wenjin Cao, Dilkrushi Hewage, Dong-Sheng Yang

Chemistry Faculty Publications

La atom reactions with 1-butene, 2-butene, and isobutene are carried out in a laser-vaporization molecular beam source. The three reactions yield the same La-hydrocarbon products from the dehydrogenation and carbon-carbon bond cleavage and coupling of the butenes. The dehydrogenated species La(C₄H₆) is the major product, which is characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectrum of La(C₄H₆) produced from the La+1-butene reaction exhibits two band systems, whereas the MATI spectra produced from the La+2-butene and isobutene reactions display only a single band system. Each of these …

Detection And Characterization Of The Tin Dihydride (Snh2 And Snd2) Molecule In The Gas Phase, Tony C. Smith, Dennis J. Clouthier

Chemistry Faculty Publications

The SnH₂ and SnD₂ molecules have been detected for the first time in the gas phase by laser-induced fluorescence (LIF) and emission spectroscopic techniques through the ùB₁–X̃¹A₁ electronic transition. These reactive species were prepared in a pulsed electric discharge jet using (CH₃)₄Sn or SnH₄/SnD₄ precursors diluted in high pressure argon. Transitions to the electronic excited state of the jet-cooled molecules were probed with LIF, and the ground state energy levels were measured from single rovibronic level emission spectra. The LIF spectrum of SnD_{2 …}

Resonant Anisotropic Emission In Rabbitt Spectroscopy, Bejan M. Ghomashi

Honors Undergraduate Theses

A variant of RABBITT pump-probe spectroscopy in which the attosecond pulse train comprises both even and odd harmonics of the fundamental IR probe frequency is explored to measure time-resolved photoelectron emission in systems that exhibit autoionizing states. It is shown that the group delay of both one-photon and two-photon resonant transitions is directly encoded in the energy-resolved photoelectron anisotropy as a function of the pump-probe time-delay. This principle is illustrated for a 1D model with symmetric zero-range potentials that supports both bound states and shape-resonances. The model is studied using both perturbation theory and solving the time-dependent Schodinger equation on …

Temperature And Lifetime Measurements In The Ssx Wind Tunnel, M. Kaur, Kaitlin D. Gelber , '20, A. D. Light, Michael R. Brown

Physics & Astronomy Faculty Works

We describe ion and electron temperature measurements in the Swarthmore Spheromak Experiment (SSX) MHD wind tunnel with the goal of understanding limitations on the lifetime of our Taylor-state plasma. A simple model based on the equilibrium eigenvalue and Spitzer resistivity predicted the lifetime satisfactorily during the first phase of the plasma evolution. We measured an average Tₑ along a chord by taking the ratio of the CIII97.7 nm to CIV155 nm line intensities using a vacuum ultraviolet (VUV) monochromator. We also recorded local measurements of Tₑ and nₑ using a double Langmuir probe in order to inform our interpretation of …

Analysis Of The Red And Green Optical Absorption Spectrum Of Gas Phase Ammonia, Nikolai F. Zobov, Phillip A. Coles, Roman I. Ovsyannikov, Aleksandra A. Kyuberis, Robert J. Hargreaves, Peter F. Bernath, Jonathan Tennyson, Sergei N. Yurchenko, Oleg L. Polyansky

Chemistry & Biochemistry Faculty Publications

Room temperature NH₃ absorption spectra recorded at the Kitt Peak National Solar Observatory in 1980 are analyzed. The spectra cover two regions in the visible: 15,200 - 15,700 cm^-1 and 17,950 - 18,250 cm^-1. These high overtone rotation-vibration spectra are analyzed using both combination differences and variational line lists. Two variational line lists were computed using the TROVE nuclear motion program: one is based on an ab initio potential energy surface (PES) while the other used a semi-empirical PES. Ab initio dipole moment surfaces are used in both cases. 95 energy levels with J = 1 …

Nuclear Magnetic Resonance Studies Of Electrode And Electrolyte Materials For Li-Ion Batteries, Lisa Cirrincione

Dissertations, Theses, and Capstone Projects

In this thesis, Nuclear Magnetic Resonance (NMR) spectroscopic techniques are used to study lithium electrode and electrolyte materials for advanced rechargeable lithium ion batteries. Three projects are described in this thesis. The first involves ²³Na and ³⁷Al static and magic angle spinning NMR studies of NaAlH₄/C anode materials for advanced rechargeable batteries. The second project is a study of paramagnetic lithium transition-metal phosphate cathode materials for Li-ion batteries, where ⁷Li, and ³¹P single crystal NMR was used in order to obtain detailed information on the local electronic and magnetic environments. The third project investigates …

Lanthanum-Mediated Dehydrogenation Of 1- And 2-Butynes: Spectroscopy And Formation Of La(C4H4) Isomers, Wenjin Cao, Dilrukshi C. Hewage, Dong-Sheng Yang

Chemistry Faculty Publications

La atom reactions with 1-butyne and 2-butyne are carried out in a laser-vaporization molecular beam source. Both reactions yield the same La-hydrocarbon products from the dehydrogenation and carbon-carbon bond cleavage and coupling of the butynes. The dehydrogenated species La(C₄H₄) is characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectra of La(C₄H₄) produced from the two reactions exhibit two identical transitions, each consisting of a strong origin band and several vibrational intervals. The two transitions are assigned to the ionization of two isomers: La(η⁴–CH₂CCCH …

Enhanced Coupling Of Light Into A Turbid Medium Through Microscopic Interface Engineering, Jonathan V. Thompson, Brett H. Hokr, Wihan Kim, Charles W. Ballmann, Brian E. Applegate, Javier Jo, Alexey Yamilov, Hui Cao, Marlan O. Scully, Vladislav V. Yakovlev

Physics Faculty Research & Creative Works

There are many optical detection and sensing methods used today that provide powerful ways to diagnose, characterize, and study materials. For example, the measurement of spontaneous Raman scattering allows for remote detection and identification of chemicals. Many other optical techniques provide unique solutions to learn about biological, chemical, and even structural systems. However, when these systems exist in a highly scattering or turbid medium, the optical scattering effects reduce the effectiveness of these methods. In this article, we demonstrate a method to engineer the geometry of the optical interface of a turbid medium, thereby drastically enhancing the coupling efficiency of …

Multispectral Identification Array, Zachary D. Eagan

Computer Engineering

The Multispectral Identification Array is a device for taking full image spectroscopy data via the illumination of a subject with sixty-four unique spectra. The array combines images under the illumination spectra to produce an approximate reflectance graph for every pixel in a scene. Acquisition of an entire spectrum allows the array to differentiate objects based on surface material. Spectral graphs produced are highly approximate and should not be used to determine material properties, however the output is sufficiently consistent to allow differentiation and identification of previously sampled subjects. While not sufficiently advanced for use as a replacement to spectroscopy the …

Spectroscopy And Formation Of Lanthanum-Hydrocarbon Radicals Formed By C—C Bond Cleavage And Coupling Of Propene, Dilrukshi C. Hewage, Wenjin Cao, Sudesh Kumari, Ruchira Silva, Tao Hong Li, Dong-Sheng Yang

Chemistry Faculty Publications

La reaction with propene is carried out in a laser-vaporization molecular beam source. Three La-hydrocarbon radicals are characterized by mass-analyzed threshold ionization (MATI) spectroscopy. One of these radicals is methylenelanthanum [La(CH₂)] (C_s), a Schrock-type metal carbene. The other two are a five-membered 1-lanthanacyclopent-3-en [La(CH₂CHCHCH₂)] (C_s) and a tetrahedron-like trimethylenemethanelanthanum [La(C(CH₂)₃)] (C_3v). Adiabatic ionization energies and metal-ligand stretching and hydrocarbon-based bending frequencies of these species are measured from the MATI spectra, preferred structures and electronic states are identified by comparing the experimental measurements and spectral …

Terahertz Molecular Spectroscopy As A Tool For Analytical Probing Of Cellular Metabolism, Mitchell Cameron Paul

Browse all Theses and Dissertations

Terahertz spectroscopy has found use as an analytical tool in determining chemical composition of exhaled human breath. This thesis demonstrates a novel application of this technology - analytical sensing of gaseous metabolic products of several types of human cell cultures. An innovative experimental system was developed for probing cellular metabolism using terahertz [THz] rotational spectroscopy. Gaseous emissions of cell cultures were analyzed and compared between several cell types. Cancerous and healthy lung cells as well as cancerous liver cells were studied. This technique carries a lot of promise as a noninvasive method of distinguishing between cell types and identifying cell …

Label-Free Raman Imaging To Monitor Breast Tumor Signatures, John Ciubuc

Open Access Theses & Dissertations

Methods built on Raman spectroscopy have shown major potential in describing and discriminating between malignant and benign specimens. Accurate, real-time medical diagnosis benefits in substantial improvements through this vibrational optical method. Not only is acquisition of data possible in milliseconds and analysis in minutes, Raman allows concurrent detection and monitoring of all biological components. Besides validating a significant Raman signature distinction between non-tumorigenic (MCF-10A) and tumorigenic (MCF-7) breast epithelial cells, this study reveals a label-free method to assess overexpression of epidermal growth factor receptors (EGFR) in tumor cells. EGFR overexpression sires Raman features associated with phosphorylated threonine and serine, and …

Micro-Spectroscopy Of Bio-Assemblies At The Single Cell Level, Jeslin Kera

Honors Undergraduate Theses

In this thesis, we investigate biological molecules on a micron scale in the ultraviolet spectral region through the non-destructive confocal absorption microscopy. The setup involves a combination of confocal microscope with a UV light excitation beam to measure the optical absorption spectra with spatial resolution of 1.4 μm in the lateral and 3.6 μm in the axial direction. Confocal absorption microscopy has the benefits of requiring no labels and only low light intensity for excitation while providing a strong signal from the contrast generated by the attenuation of propagating light due to absorption. This enables spatially resolved measurements of single …

Spectroscopic Analysis Of Neurotransmitters: A Theoretical And Experimental Raman Study, Matthew Alonzo

Open Access Theses & Dissertations

Surface-enhanced Raman spectroscopy (SERS) was applied to investigate the feasibility in the detection and monitoring of the dopamine (DA) neurotransmitter adsorbed onto silver nanoparticles (Ag NPs) at 10-11 molar, a concentration far below physiological levels. In addition, density functional theory (DFT) calculations were obtained with the Gaussian-09 analytical suite software to generate the theoretical molecular configuration of DA in its neutral, cationic, anionic, and dopaminequinone states for the conversion of computer-simulated Raman spectra. Comparison of theoretical and experimental results show good agreement and imply the presence of dopamine in all of its molecular forms in the experimental setting. The dominant …

Terahertz Molecular Spectroscopy As A Tool For Analytical Probing Of Cellular Metabolism, Mitchell Cameron Paul

Browse all Theses and Dissertations

Terahertz spectroscopy has found use as an analytical tool in determining chemical composition of exhaled human breath. This thesis demonstrates a novel application of this technology - analytical sensing of gaseous metabolic products of several types of human cell cultures. An innovative experimental system was developed for probing cellular metabolism using terahertz [THz] rotational spectroscopy. Gaseous emissions of cell cultures were analyzed and compared between several cell types. Cancerous and healthy lung cells as well as cancerous liver cells were studied. This technique carries a lot of promise as a noninvasive method of distinguishing between cell types and identifying cell …

Lime: Semiautomated Line Measurement And Identification From Stellar Spectra, Ti̇mur Şahi̇n

Turkish Journal of Physics

We present LIME (Line Measurements from ECHELLE Spectra), an IDL-based code, as a powerful tool for semiautomated stellar line measurement and identification. Interactively selected line positions (i.e. wavelengths) are compared with a master line list of the user's selections. Each unknown line that the user interactively chooses is displayed with potential identifications provided by the code in the vicinity of the selected line. The best identification is evaluated on the basis of several criteria (e.g., atomic/molecular line information, wavelength displacement, and theoretical equivalent width for solar atmospheric values). We examined the identifications by LIME in the spectra of post-red supergiant …