Physics Commons^™

Analysis Of Effects Of Macroscopic Propagation And Multiple Molecular Orbitals On The Minimum In High-Order Harmonic Generation Of Aligned Co₂, Cheng Jin, Anh-Thu Le, C. D. Lin

Physics Faculty Research & Creative Works

We report theoretical calculations of the effect of the multiple-orbital contribution in high-order harmonic generation (HHG) of aligned CO₂ with the inclusion of macroscopic propagation of harmonic fields in the medium. Our results show very good agreement with recent experiments for the dynamics of the minimum in HHG spectra as laser intensity or alignment angle changes. Calculations are carried out to check how the position of the minimum in HHG spectra depends on the degrees of molecular alignment, laser-focusing conditions, and the effects of alignment-dependent ionization rates of the different molecular orbitals. These analyses help to explain why the minima …

Forecasting The Cosmological Constraints With Anisotropic Baryon Acoustic Oscillations From Multipole Expansion, Atsushi Taruya, Shun Saito, Takahiro Nishimichi

Physics Faculty Research & Creative Works

Baryon acoustic oscillations imprinted in the galaxy power spectrum can be used as a standard ruler to determine the angular diameter distance and Hubble parameter from high-redshift galaxies. Combining redshift distortion effect which apparently distorts the galaxy clustering pattern, we can also constrain the growth rate of large-scale structure formation. Usually, future forecasts for constraining these parameters from galaxy redshift surveys are made with the full 2D power spectrum characterized as a function of wave number k and directional cosine µ between line-of-sight direction and wave vector, i.e., P(k,µ). Here, we apply the multipole expansion to the full 2D power …

Dynamics Of Equatorial Spread F Using Ground-Based Optical And Radar Measurements, Narayan P. Chapagain

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Earth's equatorial ionosphere most often shows the occurrence of large plasma density and velocity fluctuations with a broad range of scale sizes and amplitudes. These night time ionospheric irregularities in the F-region are commonly referred to as equatorial spread F (ESF) or plasma bubbles (EPBs). This dissertation focuses on analysis of ground-based optical and radar measurements to investigate the development and dynamics of ESF, which can significantly disrupt radio communication and GPS navigation systems. OI (630.0 nm) airglow image data were obtained by the Utah State University all-sky CCD camera, primarily during the equinox period, from three different longitudinal …

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, …

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 …

Low Energy (E,2e) Studies From Ch₄: Results From Symmetric Coplanar Experiments And Molecular Three-Body Distorted Wave Theory, Kate L. Nixon, Andrew James Murray, Hari Chaluvadi, Chuangang Ning, Don H. Madison

Physics Faculty Research & Creative Works

Low energy experimental and theoretical triply differential cross sections are presented for electron impact ionization of methane (CH₄) for both the highest occupied molecular orbital (HOMO) and next highest occupied molecular orbital (NHOMO). The HOMO is a predominantly p-type orbital which is labeled 1t₂ and the NHOMO is predominantly s-type labeled 2a ₁. Coplanar symmetric (symmetric both in final state electron energies and observation angles) are presented for final state electron energies ranging from 2.5 to 20 eV. The theoretical M3DW (molecular three-body distorted wave) results are in surprisingly good agreement with experiment for the HOMO …

High Dynamic Range Imaging For The Detection Of Motion., Jeffrey Robert Hay

Electronic Theses and Dissertations

High dynamic range imaging involves imaging at a bit depth higher than the typical 8-12 bits offered by standard video equipment. We propose a method of imaging a scene at high dynamic range, 14+ bits, to detect motion correlated with changes in the measured optical signal. Features within a scene, namely edges, can be tracked through a time sequence and produce a modulation in light levels associated with the edge moving across a region being sampled by the detector. The modulation in the signal is analyzed and a model is proposed that allows for an absolute measurement of the displacement …

Carbon Nanotube Growth Via Spray Pyrolysis, Robert Welch Call

Undergraduate Honors Capstone Projects

Spray pyrolysis is a promising method to create carbon nanotube forests (CNFs) on various surfaces. By injecting metallocene-hydrocarbon solutions into a heated quartz reactor, catalyst particles and carbon nanotubes can be formed simultaneously. Factors that affect CNF growth include the precursor concentration, injection rate and duration, carrier gas flow rate, substrate surface, growth temperature, and the composition of gases inside the reactor. The CNF morphologies affected by these factors will be presented and, hopefully, an optimum condition will be found.

Lidar User’S Manual, Lance William Peterson

Undergraduate Honors Capstone Projects

This is intended to be a user’s manual for the upgraded USU Rayleigh lidar. As such, it begins with a discussion of the purpose of a lidar. This is followed by a brief explanation of the fundamentals of Rayleigh scatter lidar. Next the reasons for and benefits of upgrading the lidar are discussed and as well as how the upgrade was accomplished. After establishing this basis, instructions are provided for operating the lidar, performing basic maintenance, and aligning various components.

Self-Energy Correction To The Hyperfine Splitting For Excited States, Benedikt J. Wundt, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

The self-energy corrections to the hyperfine splitting is evaluated for higher excited states in hydrogenlike ions using an expansion in the binding parameter Zα, where Z is the nuclear-charge number and α is the fine-structure constant. We present analytic results for D, F, and G states, and for a number of highly excited Rydberg states, with principal quantum numbers in the range 13≤n≤16, and orbital angular momenta =n-2 and =n-1. A closed-form analytic expression is derived for the contribution of high-energy photons, valid for any state with ≥2 and arbitrary n, , and total angular momentum j. The low-energy contributions …

A Study Of The Release Properties Of Sn And Sns From An Isol-Type Target/Ion Source System, Ronald Earl Goans

Masters Theses

Radioactive ion beams (RIBs) provide a method for studying the properties of increasingly exotic nuclei. For many nuclei, the intensity of the RIB available in the isotope separation on-line (ISOL) technique is limited by the relatively long delay time in the target/ion source system (TISS). New techniques are needed to decrease this delay time, thereby increasing the intensity of the RIBs available for study.

The sulfide molecular sideband was discovered in 2001 as a way to greatly enhance the quality of Sn beams. Holdup measurements were performed at the Holifield Radioactive Ion Beam Facility (HRIBF) to determine the extent to …

The Interplay Between Symmetry And Static Dipoles With Adsorption On Molecular Substrates, Zhengzheng Zhang

Department of Physics and Astronomy: Dissertations, Theses, and Student Research

This thesis presents evidence of preferential adsorption and the associated dipole-dipole interactions that can occur at molecule to molecule interfaces. The results are discussed in the context of the possibility of interactions caused by strong intrinsic dipoles when adsorbed on electrostatically biased substrates. Key is the discovery of lock and key adsorption chemistry by comparing the reversible absorption of the three isomers of di-iodobenzene (1,2-di-iodobenzene, 1,3-di-iodobenzene, and 1,4-di-iodobenzene) on molecular films of a quinonoid zwitterion. There is unequivocal evidence that the molecular adsorption and absorption of 1, 3-diiodobenzene is strongly favored at 150 K over the other isomers of di-iodobenzene. …

Computational Efficiency Of A Hybrid Mass Concentration And Spherical Harmonic Modeling, Nathan Piepgrass

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Through Spherical Harmonics, one can describe complex gravitational fields. However as the order and degree of the spherical harmonics increases, the computation speed rises exponentially. In addition, for onboard applications of spherical harmonics, the processors are radiation hardened in order to mitigate negative effects of the space environment on electronics. But, those processors have outdated processing speeds, resulting in a slower onboard spherical harmonic program.

This thesis examines a partial solution to the slow computation speed of spherical harmonics programs. The partial solution was to supplant the gravity models in the flight software. The spherical harmonics gravity model can be …

Surface Morphology Implications On Langmuir Probe Measurements, Padmashri Suresh

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Langmuir probes are extensively employed to study the plasmas in space and laboratory environments. Successful measurements require a comprehensive modeling of both the plasma environment and the probe conditions in the form of current collection models. In this thesis, the surface morphology implications on the probe current collection are investigated. This problem is applied and solved in the context of a CubeSat regime. The first problem that is investigated is the consequence of surface structural variability on the current measurements. A new model for dealing with non-uniformity of the probe surface structure is developed in this paper. This model is …

Electron Self-Injection Into An Evolving Plasma Bubble: Quasi-Monoenergetic Laser-Plasma Acceleration In The Blowout Regime, Serguei Y. Kalmykov, Arnaud Beck, Sunghwan A. Yi, Vladimir N. Khudik, Michael C. Downer, Erik Lefebvre, Bradley A. Shadwick, Donald P. Umstadter

Donald P. Umstadter

An electron density bubble driven in a rarefied uniform plasma by a slowly evolving laser pulse goes through periods of adiabatically slow expansions and contractions. Bubble expansion causes robust self-injection of initially quiescent plasma electrons, whereas stabilization and contraction terminate self-injection thus limiting injected charge; concomitant phase space rotation reduces the bunch energy spread. In regimes relevant to experiments with hundred terawatt- to petawatt-class lasers, bubble dynamics and, hence, the self-injection process are governed primarily by the driver evolution. Collective transverse fields of the trapped electron bunch reduce the accelerating gradient and slow down phase space rotation. Bubble expansion followed …

Electron Self-Injection Into An Evolving Plasma Bubble: Quasi-Monoenergetic Laser-Plasma Acceleration In The Blowout Regime, Serguei Y. Kalmykov, Arnaud Beck, Sunghwan A. Yi, Vladimir N. Khudik, Michael C. Downer, Erik Lefebvre, Bradley A. Shadwick, Donald P. Umstadter

Serge Youri Kalmykov

An electron density bubble driven in a rarefied uniform plasma by a slowly evolving laser pulse goes through periods of adiabatically slow expansions and contractions. Bubble expansion causes robust self-injection of initially quiescent plasma electrons, whereas stabilization and contraction terminate self-injection thus limiting injected charge; concomitant phase space rotation reduces the bunch energy spread. In regimes relevant to experiments with hundred terawatt- to petawatt-class lasers, bubble dynamics and, hence, the self-injection process are governed primarily by the driver evolution. Collective transverse fields of the trapped electron bunch reduce the accelerating gradient and slow down phase space rotation. Bubble expansion followed …

Towards A Standardized Characteristic Extraction Tool, Maria Babiuc-Hamilton

Physics Faculty Research

Knowing the precise details of the gravitational wave signature obtained from numerical simulations of binary black hole mergers is a key requirement for meaningful detection and scientific interpretation of the data. However, the waveforms are not easy to be accurately computed. The importance of this problem to the future of gravitational wave astronomy is well recognized. Cauchy-Characteristic Extraction (CCE) is the most precise and refined extraction method available. The CCE technique connects the strong-field Cauchy evolution of the spacetime near the merger to the characteristic evolution to future null infinity where the waveform is extracted in an unambiguous way. Recently, …

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, …

Two Faces Of Media While Covering Human Right Activities In India, Ratnesh Dwivedi Mr

Ratnesh Dwivedi

The situation of human rights in India is a complex one, as a result of the country's large size and tremendous diversity, its status as a developing country and a sovereign, secular, democratic republic, and its history as a former colonial territory. The Constitution of India provides for Fundamental rights, which include freedom of religion. Clauses also provide for Freedom of Speech, as well as separation of executive and judiciary and freedom of movement within the country and abroad. In its report on human rights in India during 2010, Human Rights Watch stated India had "significant human rights problems". They …

Physical Conditions In Barnard's Loop, Components Of The Orion-Eridanus Bubble, And Implications For The Warm Ionized Medium Component Of The Interstellar Medium, C. R. O'Dell, Gary J. Ferland, R. L. Porter, P. A. M. Vanhoof

Physics and Astronomy Faculty Publications

We have supplemented existing spectra of Barnard's Loop with high accuracy spectrophotometry of one new position. Cloudy photoionization models were calculated for a variety of ionization parameters and stellar temperatures and compared with the observations. After testing the procedure with recent observations of M43, we establish that Barnard's Loop is photoionized by four candidate ionizing stars, but agreement between the models and observations is only possible if Barnard's Loop is enhanced in heavy elements by about a factor of 1.4. Barnard's Loop is very similar in properties to the brightest components of the Orion-Eridanus Bubble and the warm ionized medium …