The Physics Of Moving Bodies, 2018 Nova Southeastern University

#### The Physics Of Moving Bodies, Diego Castano

*Chemistry and Physics Faculty Articles*

An alternative theoretical development of Special Relativity is presented in which Electrodynamics is not invoked. In deriving the Lorentz transformation in this manner, the existence of a maximal speed for all physical phenomena stands out. The mass-energy relation is also derived without reference to light.

Un développement théorique alternative de la relativité restreinte est présenté dans lequel l’électrodynamique n’est pas invoquée. En dérivant la transformation de Lorentz de cette manière, l’existence d’une vitesse maximale pour tous les phénomènes physiques ressort. La relation masse-énergie est également dérivée sans référence à la lumière.

Observation Of A Link Between Energy Dissipation Rate And Oscillation Frequency Of The Large-Scale Circulation In Dry And Moist Rayleigh-Bénard Turbulence, 2018 Michigan Technological University

#### Observation Of A Link Between Energy Dissipation Rate And Oscillation Frequency Of The Large-Scale Circulation In Dry And Moist Rayleigh-Bénard Turbulence, Dennis Niedermeier, Kelken Chang, Will Cantrell, Kamal Kant Chandrakar, David Ciochetto, Raymond Shaw

*Department of Physics Publications*

In this study both the small- and large-scale flow properties of turbulent Rayleigh-Bénard convection are investigated. Experiments are carried out using the Π chamber (aspect ratio Γ=2) for Rayleigh number range Ra∼10^{8}–10^{9} and Prandtl number Pr≈0.7. Furthermore, experiments are run for dry and wet conditions, i.e., top and bottom surfaces of the chamber are dry and wet, respectively. For wet conditions we further distinguish between conditions with and without the presence of sodium chloride aerosol particles which, if supersaturated conditions are achieved, lead to cloud droplet formation. We therefore refer to these ...

Development And Application Of Hybrid Wray-Agarwal Turbulence Model And Large-Eddy Simulation, 2018 Washington University in St. Louis

#### Development And Application Of Hybrid Wray-Agarwal Turbulence Model And Large-Eddy Simulation, Xu Han

*Engineering and Applied Science Theses & Dissertations*

Rapid development in computing power in past five decades along with the development and progress in building blocks of Computational Fluid Dynamics (CFD) technology has made CFD an indispensable tool for modern engineering analysis and design of fluid-based products and systems. For CFD analysis, Reynolds-Averaged Navier-Stokes (RANS) equations are currently the most widely used fluid equations in the industry. RANS methods require modeling of turbulence effect (i.e. turbulence modeling) based on empirical relations and therefore often produce low accuracy results for many flows. In recent years, the Large Eddy Simulation (LES) approach has been developed which has shown promise ...

Dualities, Topological Properties, And Degeneracies Of Classical And Quantum Lattice Models, 2018 Washington University in St. Louis

#### Dualities, Topological Properties, And Degeneracies Of Classical And Quantum Lattice Models, Seyyed Mohammad Sadegh Vaezi

*Arts & Sciences Electronic Theses and Dissertations*

We study various nontrivial facets of Ҥegeneracyӭ a concept of paramount importance in numerous physical systems.

In the first part of this thesis, we challenge the folklore that if the ground state degeneracy of a physical system depends on topology then this system must necessarily realize an unconventional, so-called Ҵopological quantumӬ order. To this end, we introduce a classical rendition of the Toric Code model that displays such a topological degeneracy yet exhibits conventional Landau order. As the ground states of this classical system may be distinguished by local measurements, this example illustrates that, on its own, topological degeneracy is ...

Topics In Pt-Symmetric Quantum Mechanics And Classical Systems, 2018 Washington University in St. Louis

#### Topics In Pt-Symmetric Quantum Mechanics And Classical Systems, Nima Hassanpour

*Arts & Sciences Electronic Theses and Dissertations*

Space-time reflection symmetry, or PT symmetry, first proposed in quantum mechanics by Bender and Boettcher in 1998 [2], has become an active research area in fundamental physics. This dissertation contains several research problems which are more or less related to this field of study. After an introduction on complementary topics for the main projects in Chap.1, we discuss about an idea which is originated from the remarkable paper by Chandrasekar et al in Chap.2. They showed that the (second-order constant-coefficient) classical equation of motion for a damped harmonic oscillator can be derived from a Hamiltonian having one degree ...

Spin Alignment Generated In Inelastic Nuclear Reactions, 2018 Washington University in St. Louis

#### Spin Alignment Generated In Inelastic Nuclear Reactions, Daniel Hoff

*Arts & Sciences Electronic Theses and Dissertations*

The spin alignment of inelastically excited 7Li projectiles, when the target remains in its ground state, was determined through angular-correlation measurements between the breakup fragments of 7Li_ (_ + t). It was found that 7Li_ is largely aligned along the beam axis (longitudinal) in this type of inelastic reaction, regardless of the target. This longitudinal alignment is well described by DWBA calculations, which can be explained by an angular-momentum-excitation-energy mismatch condition. These calculations also explain the longitudinal spin alignment of excited nuclei in several other systems, showing the phenomenon is more general. The experiment involving 7Li was performed at the Texas ...

Simulation Of Black Hole Inner Accretion Disk-Corona And Optimization Of The Hard X-Ray Polarimeter, X-Calibur, 2018 Washington University in St. Louis

#### Simulation Of Black Hole Inner Accretion Disk-Corona And Optimization Of The Hard X-Ray Polarimeter, X-Calibur, Banafsheh Beheshtipour

*Arts & Sciences Electronic Theses and Dissertations*

Mass accreting stellar mass and supermassive black holes are strong sources of X-rays. The X- ray observations enable studies of the process of black hole accretion and give us information about the spacetime background. In the framework of my thesis work, I have continued the development of a general-relativistic ray-tracing code enabling the simulation of the Comptonization of photons in the hot accretion disk corona. I use the code to investigate the impact of various approximation schemes for modeling the Comptonization finding that a fully relativistic treatment is needed for accurate predictions in the soft and hard X- ray regimes ...

In Vivo Vascular Imaging With Photoacoustic Microscopy, 2018 Washington University in St. Louis

#### In Vivo Vascular Imaging With Photoacoustic Microscopy, Hsun-Chia Hsu

*Engineering and Applied Science Theses & Dissertations*

Photoacoustic (PA) tomography (PAT) has received extensive attention in the last decade for its capability to provide label-free structural and functional imaging in biological tissue with highly scalable spatial resolution and penetration depth. Compared to modern optical modalities, PAT offers speckle-free images and is more sensitive to optical absorption contrast (with 100% relative sensitivity). By implementing different regimes of optical wavelength, PAT can be used to image diverse light-absorbing biomolecules. For example, hemoglobin is of particular interest in the visible wavelength regime owing to its dominant absorption, and lipids and water are more commonly studied in the near-infrared regime.

In ...

A Student’S Guide To Matlab For Physical Modeling, 2018 University of Pennsylvania

#### A Student’S Guide To Matlab For Physical Modeling, Philip C. Nelson, Tom Dodson

*Department of Physics Papers*

This tutorial aims to help you teach yourself enough of the Matlab programming language to get started on physical modeling, and particularly the problems appearing in Physical Models of Living Systems (Nelson, 2015). This is not an official publication of The MathWorks, Inc. We attempt to maintain it, but no claim is made that every suggestion made here will work properly with future versions of Matlab.

This is a free online document. Code listings that appear in this document, errata, and more can be found online via http://www.physics.upenn.edu/biophys/PMLS/Student ; code can also be accessed ...

Theory Of High Harmonic Generation For Probing Time-Resolved Large-Amplitude Molecular Vibrations With Ultrashort Intense Lasers, 2018 Missouri University of Science and Technology

#### Theory Of High Harmonic Generation For Probing Time-Resolved Large-Amplitude Molecular Vibrations With Ultrashort Intense Lasers, Anh-Thu Le, Toru Morishita, R. R. Lucchese, C. D. Lin

*Anh-Thu Le*

We present a theory that incorporates the vibrational degrees of freedom in a high-order harmonic generation (HHG) process with ultrashort intense laser pulses. In this model, laser-induced time-dependent transition dipoles for each fixed molecular geometry are added coherently, weighted by the laser-driven time-dependent nuclear wave packet distribution. We show that the nuclear distribution can be strongly modified by the HHG driving laser. The validity of this model is first checked against results from the numerical solution of the time-dependent Schrödinger equation for a simple model system. We show that in combination with the established quantitative rescattering theory this model is ...

Theoretical Analysis Of Dynamic Chemical Imaging With Lasers Using High-Order Harmonic Generation, 2018 Missouri University of Science and Technology

#### Theoretical Analysis Of Dynamic Chemical Imaging With Lasers Using High-Order Harmonic Generation, Van-Hoang Le, Anh-Thu Le, Rui-Hua Xie, C. D. Lin

*Anh-Thu Le*

We report theoretical investigations of the tomographic procedure suggested by Itatani et al. [Nature (London) 432, 867 (2004)] for reconstructing highest occupied molecular orbitals (HOMOs) using high-order harmonic generation (HHG). Due to the limited range of harmonics from the plateau region, we found that even under the most favorable assumptions, it is still very difficult to obtain accurate HOMO wave functions using the tomographic procedure, but the symmetry of the HOMOs and the internuclear separation between the atoms can be accurately extracted, especially when lasers of longer wavelengths are used to generate the HHG. Since the tomographic procedure relies on ...

Theoretical Study Of Photoelectron Angular Distributions In Single-Photon Ionization Of Aligned N₂ And Co₂, 2018 Missouri University of Science and Technology

#### Theoretical Study Of Photoelectron Angular Distributions In Single-Photon Ionization Of Aligned N₂ And Co₂, Cheng Jin, Anh-Thu Le, Song-Feng Zhao, R. R. Lucchese, C. D. Lin

*Anh-Thu Le*

We calculate photoelectron angular distributions (PADs) resulting from single-photon (43 eV) ionization of molecules that have been transiently aligned with a short laser pulse. The total ionization cross sections of N₂ and CO₂ vs the time delay between the aligning laser pulse and the soft x-ray photon are calculated and compared to experimental results reported by I. Thomann et al. [J. Phys. Chem. A 112, 9382 (2008)]. We present the PADs from these aligned molecules in the laboratory frame which can be compared directly with future experiments from aligned N₂ and CO₂. The alignment dependence of single-photon ionization, multiphoton ionization ...

Self-Imaging Of Molecules From Diffraction Spectra By Laser-Induced Rescattering Electrons, 2018 Missouri University of Science and Technology

#### Self-Imaging Of Molecules From Diffraction Spectra By Laser-Induced Rescattering Electrons, Junliang Xu, Zhangjin Chen, Anh-Thu Le, C. D. Lin

*Anh-Thu Le*

We study high-energy angle-resolved photoelectron spectra of molecules in strong fields. In an oscillating laser electric field, electrons released earlier in the pulse may return to recollide with the target ion, in a process similar to scattering by laboratory prepared electrons. If midinfrared lasers are used, we show that the images generated by the returning electrons are similar to images observed in typical gas-phase electron diffraction (GED). These spectra can be used to retrieve the positions of atoms in a molecule as in GED. Since infrared laser pulses of durations of a few femtoseconds are already available today, the study ...

Signature Of Ericson Fluctuations In Helium Inelastic Scattering Cross Sections Near The Double Ionization Threshold, 2018 Missouri University of Science and Technology

#### Signature Of Ericson Fluctuations In Helium Inelastic Scattering Cross Sections Near The Double Ionization Threshold, Junliang Xu, Anh-Thu Le, Toru Morishita, C. D. Lin

*Anh-Thu Le*

We calculated the inelastic electron impact excitation cross sections of He⁺ by electrons for a model helium atom to examine the onset of the signature of quantum chaotic scattering in this simple system. We find Ericson fluctuations (EF) in the calculated inelastic scattering cross sections only when the impact energies lie within about 0.21 eV below the double ionization threshold. We also discuss the stringent requirements and the proper methods for analyzing the inelastic scattering cross sections in order to observe EF experimentally.

Retrieving Transient Conformational Molecular Structure Information From Inner-Shell Photoionization Of Laser-Aligned Molecules, 2018 Missouri University of Science and Technology

#### Retrieving Transient Conformational Molecular Structure Information From Inner-Shell Photoionization Of Laser-Aligned Molecules, Xu Wang, Anh-Thu Le, Chao Yu, R. R. Lucchese, C. D. Lin

*Anh-Thu Le*

We discuss a scheme to retrieve transient conformational molecular structure information using photoelectron angular distributions (PADs) that have averaged over partial alignments of isolated molecules. The photoelectron is pulled out from a localized inner-shell molecular orbital by an X-ray photon. We show that a transient change in the atomic positions from their equilibrium will lead to a sensitive change in the alignment-averaged PADs, which can be measured and used to retrieve the former. Exploiting the experimental convenience of changing the photon polarization direction, we show that it is advantageous to use PADs obtained from multiple photon polarization directions. A simple ...

Retrieval Of Electron-Atom Scattering Cross Sections From Laser-Induced Electron Rescattering Of Atomic Negative Ions In Intense Laser Fields, 2018 Missouri University of Science and Technology

#### Retrieval Of Electron-Atom Scattering Cross Sections From Laser-Induced Electron Rescattering Of Atomic Negative Ions In Intense Laser Fields, Xiaoxin Zhou, Zhangjin Chen, Toru Morishita, Anh-Thu Le, C. D. Lin

*Anh-Thu Le*

We investigated the two-dimensional electron momentum distributions of atomic negative ions in an intense laser field by solving the time-dependent Schrödinger equation (TDSE) and using the first- and second-order strong-field approximations (SFAs). We showed that photoelectron energy spectra and low-energy photoelectron momentum distributions predicted from SFAs are in reasonable agreement with the solutions from the TDSE. More importantly, we showed that accurate electron-atom elastic scattering cross sections can be retrieved directly from high-energy electron momentum spectra of atomic negative ions in the laser field. This opens up the possibility of measuring electron-atom and electron-molecule scattering cross sections from the photodetachment ...

Quantitative Rescattering Theory Of High-Order Harmonic Generation For Polyatomic Molecules, 2018 Missouri University of Science and Technology

#### Quantitative Rescattering Theory Of High-Order Harmonic Generation For Polyatomic Molecules, Anh-Thu Le, R. R. Lucchese, C. D. Lin

*Anh-Thu Le*

We report applications of the quantitative rescattering theory (QRS) for calculation of high-order-harmonic generation (HHG) from polyatomic molecules in ultrashort linearly polarized intense laser pulses, using the example of the CCl₄ molecule. In particular, we present a detailed analysis and a treatment for the phase of the electron returning wave packet, which recollides with the parent molecular ion to emit high-energy photons. Our results show that Cooper-type minimum structures in the molecular photoionization cross section lead to quite distinguishable minima in the HHG spectra, even for unaligned polyatomic molecules.

Reconstruction Of Two-Dimensional Molecular Structure With Laser-Induced Electron Diffraction From Laser-Aligned Polyatomic Molecules, 2018 Missouri University of Science and Technology

#### Reconstruction Of Two-Dimensional Molecular Structure With Laser-Induced Electron Diffraction From Laser-Aligned Polyatomic Molecules, Chao Yu, Hui Wei, Xu Wang, Anh-Thu Le, Ruifeng Lu, C. D. Lin

*Anh-Thu Le*

Imaging the transient process of molecules has been a basic way to investigate photochemical reactions and dynamics. Based on laser-induced electron diffraction and partial one-dimensional molecular alignment, here we provide two effective methods for reconstructing two-dimensional structure of polyatomic molecules. We demonstrate that electron diffraction images in both scattering angles and broadband energy can be utilized to retrieve complementary structure information, including positions of light atoms. With picometre spatial resolution and the inherent femtosecond temporal resolution of lasers, laser-induced electron diffraction method offers significant opportunities for probing atomic motion in a large molecule in a typical pump-probe measurement.

Protonium Formation In The P̅-H Collision At Low Energies By A Diabatic Approach, 2018 Missouri University of Science and Technology

#### Protonium Formation In The P̅-H Collision At Low Energies By A Diabatic Approach, M. Hesse, Anh-Thu Le, C. D. Lin

*Anh-Thu Le*

We present a diabatization technique in combination with the recently developed hyperspherical close coupling (HSCC) method. In contrast to the strict diabatization, our simple diabatization procedure transforms *only* sharp avoided crossings in the adiabatic hyperspherical potential curves into real crossings. With this approach, the weak collision channels can be removed from the close-coupling calculations. This method is used to study the antiproton-hydrogen collision at low energies. In the case of a scaled down (anti)proton mass, we show that a 10-channel calculation is enough to obtain converged cross sections at low energies. The results also indicate that protonium formation occurs ...

Probing And Extracting The Structure Of Vibrating Sf₆ Molecules With Inner-Shell Photoelectrons, 2018 Missouri University of Science and Technology

#### Probing And Extracting The Structure Of Vibrating Sf₆ Molecules With Inner-Shell Photoelectrons, Ngoc-Ty Nguyen, R. R. Lucchese, C. D. Lin, Anh-Thu Le

*Anh-Thu Le*

We propose a scheme for probing the structure of vibrating molecules with photoelectrons generated from ultrashort soft-x-ray pulses. As an example we analyze below-100-eV photoelectrons liberated from the S(2p) orbital of vibrating SF₆ molecules to image very small structural changes of molecular vibration. In particular, photoionization cross sections and photoelectron angular distributions (PAD) at nonequilibrium geometries can be retrieved accurately with photoelectrons near the shape resonance at 13 eV. This is achieved with a pump-probe scheme, in which the symmetric stretch mode is first Raman excited predominantly by a relatively short laser pulse and then later probed at different ...