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Full-Text Articles in Physics

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 ...


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 ...


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 ...


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 ...


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 ...


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 ...