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Full-Text Articles in Physics

Conformational Dependence Of Σ-Electron Delocalization In The Catenae Xnme2n+2, X = Si, Ge, Sn, And Pb, Milena Jovanovic Jan 2019

Conformational Dependence Of Σ-Electron Delocalization In The Catenae Xnme2n+2, X = Si, Ge, Sn, And Pb, Milena Jovanovic

Chemistry Graduate Theses & Dissertations

Bonds of σ type are the most common chemical bonds, dominating bonding in all molecules and defining the framework of a molecule. It has been long known that electrons in σ bonds can delocalize throughout a molecule. However, the nature of σ-electron delocalization is not fully understood due to its complexity. One of the important aspects of σ-electron delocalization is its conformational dependence, first noted in oligosilanes where properties of a molecule change drastically when it changes conformation. This dissertation describes efforts to understand the conformational dependence of σ delocalization in oligosilanes and their heavier analogs using simple intuitive models ...


The Role Of Defects On The Optical, Electronic, And Magnetic Properties Of Iron-Sulfur Solids, Alyssa Ruth Landin Jan 2018

The Role Of Defects On The Optical, Electronic, And Magnetic Properties Of Iron-Sulfur Solids, Alyssa Ruth Landin

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Solids composed of iron and sulfur are earth abundant and nontoxic, and can exhibit interesting and technologically important optical, electronic, and magnetic phenomena. Troilite (hexagonal FeS) is predicted to exhibit large room temperature magnetoelectricity and may exhibit high temperature superconducting properties, and pyrite (cubic FeS2) is a promising candidate for photovoltaic

applications. However, defects naturally occur within both of these solids. Troilite contains Fe deficiencies with atomic formula Fe(1-x)S, while pyrite contains sulfur deficiencies with the atomic formula FeS(2-x). The Fe-S phase diagram is congested in these regions of slight non-stoichiometries, and even when the atomic ...


Velocity-Map Imaging Photoelectron Spectroscopy Of Small Molecular Anions, Allan Maple De Oliveira Jan 2018

Velocity-Map Imaging Photoelectron Spectroscopy Of Small Molecular Anions, Allan Maple De Oliveira

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Gas phase anion photoelectron spectroscopy presents an opportunity for investigating molecules that are inaccessible by other experimental techniques, by providing data on the structure, reactivity and energetics of short-lived radicals and transition state species. Our recent development of a novel, plasma entrainment source of cold, weakly-bound anions opens a door to new exotic species to be investigated. In this thesis, I explore the capabilities of photoelectron spectroscopy and its application to small exotic molecular anions, while further developing and employing the novel dual-valve ion source.

The thesis begins with a brief history of photoelectron spectroscopy, followed by a description of ...


Analytical Modeling And Numerical Simulations Of Time Delays In Attosecond Streaking Of One- And Two-Photon Ionization, Cory Scott Goldsmith Jan 2018

Analytical Modeling And Numerical Simulations Of Time Delays In Attosecond Streaking Of One- And Two-Photon Ionization, Cory Scott Goldsmith

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

The generation of attosecond-duration (1 as = 10-18 s) coherent light through the process of high-order harmonic generation has opened the perspective for probing fundamental processes, such as photoionization, on the natural timescale of electron dynamics in matter. One probing technique is the attosecond streaking method, in which the momentum of the photoelectron is measured as a function of the time delay between the ionizing, attosecond extreme ultraviolet (XUV) pulse, and a weak, femtosecond near-infrared (NIR) pulse which streaks the momentum of the photoelectron, known as a streaking trace. The observed trace contains time information about the photoionization process in ...


Nonadiabatic Multielectron Dynamics In Interaction Of Molecules With Intense Laser Pulses, Andres F. Mora Jan 2018

Nonadiabatic Multielectron Dynamics In Interaction Of Molecules With Intense Laser Pulses, Andres F. Mora

Undergraduate Honors Theses

Ultrashort high intensity laser pulses have allowed for the observation of ultrafast dynamics in atoms and molecules. Due to the complexity, these multielectron systems interacting with ultrashort intense laser fields are often theoretically studied using the single active electron approximation (SAE). We present here results of simulations within Time Dependent Density Functional Theory which address the multielectron nature of the studied systems. The results exhibit multielectron effects in form of orbital coupling and non-adiabatic electron dynamics in electron localization, high harmonic generation and ionization of N+ 2 interacting with a strong laser pulse.


Photoelectron Spectroscopy Of Organic Aromatic Anions, Daniel John Nelson Jan 2017

Photoelectron Spectroscopy Of Organic Aromatic Anions, Daniel John Nelson

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Nelson, Daniel John (Ph.D. Chemical Physics)

Photoelectron Spectroscopy of Organic Aromatic Anions

Thesis directed by Professor W. Carl Lineberger

This dissertation reports and interprets the results of experiments in which photoelectron spectroscopy was performed on a variety of aromatic anions. In addition to these photoelectron studies, the results and conclusions of an experiment in which HCl is scattered off atomically flat Au (111) surfaces are also presented.

Photoelectron spectroscopy of the isomers of methylphenoxide reveals that these molecules display minimal vibrational excitation upon photodetachment, accessing the electronic ground and first excited state of the corresponding radicals. The photoelectron spectra ...


Elastic Interactions Between Optical And Topological Solitons In Chiral Nematic Liquid Crystal, Andy Seracuse Jan 2017

Elastic Interactions Between Optical And Topological Solitons In Chiral Nematic Liquid Crystal, Andy Seracuse

Undergraduate Honors Theses

The research presented in this thesis investigates the elastic director field interactions between optical, spatial solitons and defect structures in frustrated chiral nematic liquid crystals. I characterize experimentally the rich elastic interactions between torons, particle-like localized director field configurations with non-trivial topology, and spatial, optical solitons, which have been previously dubbed nematicons. By exploitation of the waveguide regime for the generation of stable thresholdless nematicons via the reorientational nonlinearity present in thermotropic liquid crystals, I characterize the elastic potential energy surrounding a stationary nematicon and a mobile toron via measurement of toron displacement as a function of time. I compare ...


Design And Construction Of A 3d Velocity Map Imaging Spectrometer, Laura Wooldridge Jan 2017

Design And Construction Of A 3d Velocity Map Imaging Spectrometer, Laura Wooldridge

Undergraduate Honors Theses

Enormous insight can be gained into high energy molecular processes by ionizing a molecule and examining the energy release of the resulting ions and electrons. Time-of-flight spectroscopy is a simple and powerful technique for measuring the mass-to-charge ratio and initial energy of a particle by recording the time it takes to accelerate through a region. Velocity map imaging (VMI) is a newer technique that measures the kinetic energy and angular distributions of electrons and ions in the form of a 2D spatial image. VMI spectrometers can now be combined with time-of-flight techniques to extract the entire three-dimensional momentum distribution of ...


Pyrolysis And Spectroscopy Of Cyclic Aromatic Combustion Intermediates, Grant Thornton Buckingham Jan 2016

Pyrolysis And Spectroscopy Of Cyclic Aromatic Combustion Intermediates, Grant Thornton Buckingham

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

We have studied the pyrolysis of aromatic combustion intermediates using an array of detection techniques. The molecules investigated include cyclic aromatic molecules with hydrocarbon substituents (ethylbenzene, n-propylbenzene, isopropylbenzene, and styrene), oxygen-containing substituents (anisole and phenol), triply substituted systems (vanillin), resonance stabilized radicals (benzyl radical and tropyl radical) and phenyl radical. At the exit of a resistively heated micro-reactor (1 mm inner diameter, 3 cm long), the pyrolysis fragments are detected using photoionization mass spectrometry (PIMS), matrix isolation vibrational spectroscopy, microwave spectroscopy, tunable VUV synchrotron-based PIMS, and table-top VUV PIMS with photoelectron photoion coincidence spectroscopy (PEPICO). This array of detection methods ...


Active Pattern Formation In One And Two Dimensions, Hui-Shun Kuan Jan 2016

Active Pattern Formation In One And Two Dimensions, Hui-Shun Kuan

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

In this thesis, we studied active systems in one or two dimensions in which particles are self-propelled and repel each other. In one-dimensional models, we considered driven particles on single lanes or in anti-parallel overlaps with both binding/unbinding and switching between the lanes. These models are inspired by experiments on kinesin proteins walking on microtubules or anti-parallel overlaps. In the single-lane case, we focused on length regulation controlled by end concentration or flux. In the anti-parallel overlap case, we used a phase space flow method to determine the density profiles and compared the analytic results with kinetic Monte Carlo ...


Ultrafast Nonlinear Spectroscopy Of Red Fluorescent Proteins, Patrick Eugene Konold Jan 2015

Ultrafast Nonlinear Spectroscopy Of Red Fluorescent Proteins, Patrick Eugene Konold

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Red-emitting homologues (RFPs) of the native Green Fluorescent Protein (GFP) with emission wavelengths beyond 650 nm are desirable probes for in vivo imaging experiments. They offer the potential for deeper tissue penetration and lower background scatter given a cleaner spectral window. However, bioimaging applications are hindered by poor photophysics (e.g. low fluorescence quantum yield, high photobleaching), which limits experimental resolution and represents a significant obstacle towards utilization for low copy-number, long-duration imaging applications. In this thesis, a variety of femtosecond nonlinear electronic spectroscopies were employed jointly with site-directed mutagenesis to investigate the photophysical properties of RFPs. In one study ...


Techniques In Molecular Spectroscopy: From Broad Bandwidth To High Resolution, Kevin C. Cossel Jan 2014

Techniques In Molecular Spectroscopy: From Broad Bandwidth To High Resolution, Kevin C. Cossel

Physics Graduate Theses & Dissertations

This thesis presents a range of different experiments all seeking to extended the capabilities of molecular spectroscopy and enable new applications. The new technique of cavity-enhanced direct frequency comb spectroscopy (CE-DFCS) provides a unique combination of broad bandwidth, high resolution, and high sensitivity that can be useful for a wide range of applications. Previous demonstrations of CE-DFCS were confined to the visible or near-infrared and operated over a limited bandwidth: for many applications it is desirable to increase the spectral coverage and to extend to the mid-infrared where strong, fundamental vibrational modes of molecules occur. There are several key requirements ...


From Material Design To Device: Structural And Thermodynamic Considerations For Solid-Phase Lithium-Ion Electrolytes, Brian E. Francisco Jan 2014

From Material Design To Device: Structural And Thermodynamic Considerations For Solid-Phase Lithium-Ion Electrolytes, Brian E. Francisco

Mechanical Engineering Graduate Theses & Dissertations

Too often, we check the battery status of our favorite gadget and wonder: "Is it going to make it?" At some point in the not-so-distant future, I believe we will not have to ask this question. Until then, it is the incremental movement of the boundaries of our understandings of energy storage sciences that bring us closer to the next breakthrough technology.

In this thesis, we investigate a material which may one day play a key role in enabling fast-charging, long-lasting energy storage devices: the solid-state electrolyte. While this material has begun to replace liquid electrolytes in batteries, we envisioned ...


Photodissociation Spectroscopy Of Anionic Transition Metal Complexes, Sydney Hamilton Kaufman Jan 2013

Photodissociation Spectroscopy Of Anionic Transition Metal Complexes, Sydney Hamilton Kaufman

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Transition metal complexes play an important role in many aspects of chemistry; whether in supporting biological functions, as catalysts for organic reactions, in the environment, or in industry. This thesis is comprised of gas-phase spectroscopic studies of four transition metal species with implications for many different chemical applications.

Most knowledge of the target molecules in this thesis are derived from studies in the condensed phase, where the chemical environment can change molecular properties. As a result, it is difficult to gain an understanding of the intrinsic properties in solution as well as a molecular-level picture of chemical reactions that take ...


Enabling Two-Dimensional Fourier Transform Electronic Spectroscopy On Quantum Dots, Robert John Hill Jr. Jan 2013

Enabling Two-Dimensional Fourier Transform Electronic Spectroscopy On Quantum Dots, Robert John Hill Jr.

Physics Graduate Theses & Dissertations

Colloidal semiconductor nanocrystals exhibit unique properties not seen in their bulk counterparts. Quantum confinement of carriers causes a size-tunable bandgap, making them attractive candidates for solar cells. Fundamental understanding of their spectra and carrier dynamics is obscured by inhomogeneous broadening arising from the size distribution. Because quantum dots have long excited state lifetimes and are sensitive to both air and moisture, there are many potential artifacts in femtosecond experiments. Two-dimensional electronic spectroscopy promises insight into the photo-physics, but required key instrumental advances. Optics that can process a broad bandwidth without distortion are required for a two-dimensional optical spectrometer. To control ...


Bringing Two-Dimensional Fourier Transform Electronic Spectroscopy Into The Short-Wave Infrared, Trevor Laurence Courtney Jan 2012

Bringing Two-Dimensional Fourier Transform Electronic Spectroscopy Into The Short-Wave Infrared, Trevor Laurence Courtney

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Two-dimensional Fourier Transform (2D FT) spectroscopy in the short-wave infrared (1-2 &mu) enables high frequency and time resolution experiments of molecular dyes, third-generation photovoltaic systems, and carotenoids - all rich in electronic transitions in this spectral region. Such experiments require short pulses with broad spectra to probe fast dephasing or solvation dynamics as well as couplings between widely spaced electronic transitions. Stable, low-dispersion interferometers at Brewster's angle are introduced for multioctave-spanning nonlinear spectroscopies. We adapt a compact, phase-characterized Mach-Zehnder interferometer to the short-wave infrared; active stabilization produces accurate and evenly spaced time delays between the two excitation pulses in 2D FT spectroscopy. An intrinsically phase-stable Sagnac interferometer is introduced to enhance the interferometric signal detection with respect to the copropagating local oscillator in partially collinear 2D FT spectroscopy. These interferometers exploit the air-glass interface Brewster's angle of thin-film metallic beam splitters to preserve expected output phase shifts and to minimize secondary reflections over multiple octaves. A homebuilt short-wave IR noncollinear optical parametric amplifier with a periodically poled crystal provides broadband excitation and ...


Nanostructures Of Liquid Crystal Phases, Dong Chen Jan 2012

Nanostructures Of Liquid Crystal Phases, Dong Chen

Physics Graduate Theses & Dissertations

Bent-core liquid crystals have attracted intense interest in recent years, exhibiting a wide variety of novel structural phenomena involving the interplay of chirality, molecular bend and molecular tilt. Freeze-fracture transmission electron microscopy together with other experimental methods has been used to characterize the nanostructures of bent-core liquid crystal phases in which the molecules undergo complex self-assembly, forming, for example, helical nanofilaments (the B4 phase), disordered focal conics (the DC phase), and layer undulations (the B7 phase) in the bulk. These studies have helped us better understand the complex nature of these and other liquid crystal phases. For example, the investigation ...


Elucidation Of Ultrafast Photophysics With Optical Pulse Shaping, Erik Martin Grumstrup Jan 2011

Elucidation Of Ultrafast Photophysics With Optical Pulse Shaping, Erik Martin Grumstrup

Physics Graduate Theses & Dissertations

Optical pulse shaping is an incisive tool of laser spectroscopy that allows the experimentalist extensive flexibility to manipulate the electric field of an excitation laser pulse. In this thesis, four applications of optical pulse shaping are examined. In Chapter 2, a partially non-collinear implementation of two-dimensional electronic spectroscopy is demonstrated for the first time on rubidium vapor. The use of a pulse shaper in this context is advantageous as it significantly reduces the complexity of the experimental apparatus. Unfortunately, non-ideal pulse shaping due to pixelation effects in some pulse-shaping devices leads to spurious pulse generation when the spatial masks become ...


Electronic Photodissociation Spectroscopy Of Electrosprayed Anions, Jesse Cohen Marcum Jan 2011

Electronic Photodissociation Spectroscopy Of Electrosprayed Anions, Jesse Cohen Marcum

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

Ionic compounds are ubiquitous and play central roles in a variety of chemical, physical, and biological processes. Due to the incredible complexity of many of these processes, it is advantageous to develop a detailed molecular-level description of ions as isolated species. This approach provides the ability to study the intrinsic properties of ions in the absence of perturbing effects from solvent and/or counterions. Additionally, such studies can be used to perform experiments on model systems in which ions serve as “molecular laboratories” for developing new insight to fundamental physical and chemical phenomena.

This thesis is comprised of work I ...


Thermochemical Conversion Of Biomass: A Molecular Viewpoint, Angayle Konstance Vasiliou Jan 2011

Thermochemical Conversion Of Biomass: A Molecular Viewpoint, Angayle Konstance Vasiliou

Chemistry & Biochemistry Graduate Theses & Dissertations (1986-2018)

This dissertation describes experiments performed to study the thermal decomposition of biomass from a molecular viewpoint. The structure of biomass consists of three major parts: cellulose, hemicellulose and lignin. Thermochemical conversion of biomass, specifically pyrolysis and gasification, yields a complex mixture of light gases, condensable vapors and aromatic tars. The goal for the gasification of biomass is to maximize the production of syngas (CO and H2 ) and minimize the production of aromatic tars. This thesis provides thermochemical information particularly related to cellulose decomposition.

The current technology for the conversion of biomass to biofuels is hindered by the lack of fundamental ...


Photoelectron Spectroscopy Of Nitroalkane Anions, Christopher Lynn Adams Jan 2011

Photoelectron Spectroscopy Of Nitroalkane Anions, Christopher Lynn Adams

Physics Graduate Theses & Dissertations

This thesis describes research on the electronic properties of nitroalkane anions, CH3(CH2)nNO2 (where n=0,1,2, and 3), using a newly built velocity-map imaging photoelectron spectrometer. The nitroalkanes are an intriguing class of molecules that possess many similarities owing to the dominating presence of the nitro group. They all possess relatively low adiabatic electron affinities, large dipole moments, and undergo similar distortions (largely localized within the nitro group) upon electron attachment. The focus of the studies presented in this thesis is quantitatively characterizing the anion and neutral states, determining fundamental molecular properties (i ...