High-Resolution Movies Of Molecular Rotational Dynamics Captured With Ultrafast Electron Diffraction,
2020
University of Nebraska–Lincoln
High-Resolution Movies Of Molecular Rotational Dynamics Captured With Ultrafast Electron Diffraction, Yanwei Xiong, Kyle J. Wilkin, Martin Centurion
Martin Centurion Publications
Imaging the structure of molecules during a photoinduced reaction is essential for elucidating reaction mechanisms. This requires high spatiotemporal resolution to capture nuclear motions on the femtosecond and subangstrom scale, and a sufficiently high signal level to sample their continuous evolution with high fidelity. Here we show that, using high-repetition-rate ultrafast electron diffraction, we can accurately reconstruct a movie of the coherent rotational motion of laser-aligned nitrogen molecules. We have used a tabletop 90-keV photoelectron gun to simultaneously achieve high temporal resolution of 240 fs full width at half maximum and an electron beam current that is more than an …
Toughening A Superstrong Carbon Crystal: Sequential Bond-Breaking Mechanisms,
2020
Jilin University
Toughening A Superstrong Carbon Crystal: Sequential Bond-Breaking Mechanisms, Hui Liang, Hefei Li, Quan Li, Changfeng Chen
Physics & Astronomy Faculty Research
A complex orthorhombic carbon allotrope in Pbam symmetry with 32 atoms in its unit cell, thus termed Pbam-32 carbon, was recently predicted [C. Y. He et al., Phys. Rev. Lett. 121, 175701 (2018)]. Its crystal structure comprises alternating fivefold, sixfold, and sevenfold carbon rings and exhibits reduced bonding anisotropy compared to diamond, raising the prospects of finding a superstrong material with distinct and favorable mechanical properties. Here we report findings from first-principles calculations that reveal peculiar stress-strain relations in Pbam-32 carbon. The obtained stress responses under various tensile and shear strains display outstanding characteristics contrasting those of traditional superhard materials …
Schrödinger-Pauli Theory Of Electrons: New Perspectives,
2020
CUNY Brooklyn College
Schrödinger-Pauli Theory Of Electrons: New Perspectives, Viraht Sahni
Publications and Research
The Schrödinger-Pauli (SP) theory of electrons in an electromagnetic field explicitly accounts for the electron spin moment. The many-electron theory is complemented via a new descriptive perspective viz. that of the individual electron via its equation of motion or ‘Quantal Newtonian’ first law. The law is in terms of ‘classical’ fields whose sources are quantum mechanical expectation values of Hermitian operators taken with respect to the system wave function. The law states that each electron experiences an external and an internal field, the sum of which vanish. The external field is the sum of the binding electrostatic and a Lorentz …
A Fully Quantum Calculation Of Broadening And Shifting Coefficients Of The D1 And D2 Spectral Lines Of Alkali-Metal Atoms Colliding With Noble-Gas Atoms,
2020
Air Force Institute of Technology
A Fully Quantum Calculation Of Broadening And Shifting Coefficients Of The D1 And D2 Spectral Lines Of Alkali-Metal Atoms Colliding With Noble-Gas Atoms, Robert D. Loper, David E. Weeks
Faculty Publications
We use the Baranger model to compute collisional broadening and shift rates for the D1 and D2 spectral lines of M + Ng, where M = K, Rb, Cs and Ng = He, Ne, Ar. Scattering matrix elements are calculated using the channel packet method, and non-adiabatic wavepacket dynamics are determined using the split-operator method together with a unitary transformation between adiabatic and diabatic representations. Scattering phase shift differences are weighted thermally and are integrated over temperatures ranging from 100 K to 800 K. We find that predicted broadening rates compare well with experiment, but shift rates are …
Indium Segregation To The Selvedge Of In4Se3 (001),
2020
University of Nebraska–Lincoln
Indium Segregation To The Selvedge Of In4Se3 (001), Archit Dhingra, Zoe G. Marzouk, Esha Mishra, Pavlo V. Galiy, Taras M. Nenchuk, Peter Dowben
Peter Dowben Publications
Thermal motion of the surface atoms will lead to a decrease in photoemission intensity, while surface segregation may result in an increase of some phostoemission intensities. For In4Se3(001), both effects are seen. The Debye–Waller factor plot, based on the temperature dependent X-ray photoemission spectroscopy (XPS) measurements on In4Se3(001), suggests an upper bound of 203 ± 6 K for the effective Debye temperature, based on the surface component of the In 3d5/2 core-level. Indium is found to segregate to selvedge (subsurface region) of the crystal.
Physics-Constrained Hyperspectral Data Exploitation Across Diverse Atmospheric Scenarios,
2020
Air Force Institute of Technology
Physics-Constrained Hyperspectral Data Exploitation Across Diverse Atmospheric Scenarios, Nicholas M. Westing
Theses and Dissertations
Hyperspectral target detection promises new operational advantages, with increasing instrument spectral resolution and robust material discrimination. Resolving surface materials requires a fast and accurate accounting of atmospheric effects to increase detection accuracy while minimizing false alarms. This dissertation investigates deep learning methods constrained by the processes governing radiative transfer to efficiently perform atmospheric compensation on data collected by long-wave infrared (LWIR) hyperspectral sensors. These compensation methods depend on generative modeling techniques and permutation invariant neural network architectures to predict LWIR spectral radiometric quantities. The compensation algorithms developed in this work were examined from the perspective of target detection performance using …
Low-Information Radiation Imaging Using Rotating Scatter Mask Systems And Neural Network Algorithms,
2020
Air Force Institute of Technology
Low-Information Radiation Imaging Using Rotating Scatter Mask Systems And Neural Network Algorithms, Robert J. Olesen
Theses and Dissertations
While recent studies have demonstrated the directional capabilities of the single-detector rotating scatter mask (RSM) system for discrete, dual-particle environments, there has been little progress towards adapting it as a true imaging device. In this research, two algorithms were developed and tested using an RSM mask design previously optimized for directional detection and simulated 137Cs signals from a variety of source distributions. The first, maximum-likelihood expectation-maximization (ML-EM), was shown to generate noisy images, with relatively low accuracy (145% average relative error) and signal-to-noise ratio (0.27) for most source distributions simulated. The second, a novel regenerative neural network (ReGeNN), performed exceptionally …
Long‐Term Variations Of Quasi‐Trapped And Trapped Electrons In The Inner Radiation Belt Observed By Demeter And Sampex,
2020
University of Colorado Boulder
Long‐Term Variations Of Quasi‐Trapped And Trapped Electrons In The Inner Radiation Belt Observed By Demeter And Sampex, Kun Zhang, Xinlin Li, Zheng Xiang, Leng Ying Khoo, Hong Zhao, Mark D. Looper, Michael A. Temerin, Jean-Andre Sauvaud
Publications
Electrons in the Earth's radiation belts can be categorized into three populations: precipitating, quasi‐trapped, and trapped. We use data from the Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) and Solar, Anomalous, and Magnetospheric Particle Explorer satellite (SAMPEX) missions and from ground‐based neutron monitors (NM) and sunspot observations to investigate the long‐term variation of quasi‐trapped and trapped sub‐MeV electrons on different L shells in the inner belt. DEMETER and SAMPEX measurements span over 17 years and show that at L ≤ 1.14 the electron flux is anticorrelated with sunspot number, but proportional to the cosmic ray intensity represented by …
H-Atom Ladder Operator Revisited,
2020
University of Connecticut
H-Atom Ladder Operator Revisited, Carl W. David
Chemistry Education Materials
An error laden note (Am. J. Phys., 34, 984,(1966)) concerning the ladder operator solution to the hydrogen atom electronic energy levels is corrected.
A Hybrid Achromatic Metalens,
2020
University of Kentucky
A Hybrid Achromatic Metalens, Fatih Balli, Mansoor A. Sultan, Sarah K. Lami, J. Todd Hastings
Electrical and Computer Engineering Faculty Publications
Metalenses, ultra-thin optical elements that focus light using subwavelength structures, have been the subject of a number of recent investigations. Compared to their refractive counterparts, metalenses offer reduced size and weight, and new functionality such as polarization control. However, metalenses that correct chromatic aberration also suffer from markedly reduced focusing efficiency. Here we introduce a Hybrid Achromatic Metalens (HAML) that overcomes this trade-off and offers improved focusing efficiency over a broad wavelength range from 1000-1800 nm. HAMLs can be designed by combining recursive ray-tracing and simulated phase libraries rather than computationally intensive global search algorithms. Moreover, HAMLs can be fabricated …
Dynamic Monte Carlo Modeling Of Protein-Dna Interactions,
2020
University of Northern Iowa
Dynamic Monte Carlo Modeling Of Protein-Dna Interactions, Aaron Kirchman, Ali Tabei
Summer Undergraduate Research Program (SURP) Symposium
No abstract provided.
Analyzing And Classifying Single Molecule Microscopy Data,
2020
University of Northern Iowa
Analyzing And Classifying Single Molecule Microscopy Data, Troy Buzynski, Ali Tabei
Summer Undergraduate Research Program (SURP) Symposium
No abstract provided.
Modeling The Griffiths Phase In Manganese Intercalated Tantalum Disulfide [Slides],
2020
University of Northern Iowa
Modeling The Griffiths Phase In Manganese Intercalated Tantalum Disulfide [Slides], Aaron Janaszak, Lukas Stuelke, Paul Shand
Undergraduate Student Work
The Griffiths Phase is a result of a spontaneous increase in the overall magnetization of the system primarily influenced by the rare, large clusters transitioning to a ferromagnetic state at the Curie Temperature. We were able to create a MATLAB program that exhibits this trend by using the Langevin function to simulate clusters.
Site Selective Adsorption Of The Spin Crossover Complex Fe(Phen)2(Ncs)2 On Au(111),
2020
University of Nebraska-Lincoln
Site Selective Adsorption Of The Spin Crossover Complex Fe(Phen)2(Ncs)2 On Au(111), Sumit Beniwal, Suchetana Sarkar, Felix Baier, Birgit Weber, Peter Dowben, Axel Enders
Peter Dowben Publications
The iron(II) spin crossover complex Fe(1,10-phenanthroline)2(NCS)2, dubbed Fe-phen, has been studied with scanning tunneling microscopy, after adsorption on the 'herringbone' reconstructed surface of Au(111) for sub-monolayer coverages. The Fe-phen molecules attach, through their NCS-groups, to the Au atoms of the fcc domains of the reconstructed surface only, thereby lifting the herringbone reconstruction. The molecules stack to form 1D chains, which run along the Au[110] directions. Neighboring Fe-phen molecules are separated by approximately 2.65 nm, corresponding to 9 atomic spacings in this direction. The molecular axis, defined by the two phenanthroline groups, is aligned perpendicular to the …
Generation Of Correlated Dual Frequency Combs With Pm Fiber Lasers For High-Precision Metrology,
2020
Center for High Technology Materials
Generation Of Correlated Dual Frequency Combs With Pm Fiber Lasers For High-Precision Metrology, Hanieh Afkhamiardakani
Optical Science and Engineering ETDs
Intracavity Phase Interferometry (IPI) using two correlated, counter-propagating frequency combs (pulse trains) in mode-locked lasers has evolved into a powerful technique for high-precision metrology. In this method a physical parameter to be measured imparts a phase shift onto a pulse circulating in the laser cavity. Inside a laser cavity, that phase shift becomes a frequency shift (phase shift/round-trip time) applied to the whole frequency comb created by this pulse as it exits the cavity at each round-trip. This frequency shift is measured by interfering this comb with a reference comb created by a reference pulse circulating in the same mode-locked …
Radiation-Balanced Fiber Lasers And Amplifiers,
2020
University of New Mexico
Radiation-Balanced Fiber Lasers And Amplifiers, Esmaeil Mobini Souchelmaei Mr
Optical Science and Engineering ETDs
Over the past decades, high-power fiber lasers and amplifiers have been extensively under research to achieve higher output powers. However, temperature rise in the core of fiber lasers and amplifiers has been a big issue in power-scaling. Radiation-balancing is a viable technique introduced for effective heat mitigation in lasers and amplifiers by S. Bowman in 1995. Radiation-balancing relies on solid-state laser cooling as a self-cooling mechanism to mitigate the generated heat in lasers and amplifiers. To implement the mentioned idea in fiber lasers and amplifiers, a set of issues should be scrutinized; (i) the amenability of silica glass (as the …
Quantum Two-Photon Laser In Kerr-Like Medium,
2020
Universiti Malaya
Quantum Two-Photon Laser In Kerr-Like Medium, Ahmed Mathkoor Faisal Hamood
Student Works (2020-2029)
In this thesis, we studied the Kerr nonlinearity effects on nonclassicality and statistics of the laser field besides the effects of detuning, injection rate, and intensity-dependent coupling (IDC). We developed a quantum theory of light generated from a two-photon laser (TPL) with nonlinear Kerr-like medium in a laser dissipative cavity. The full quantum mechanical approach with the density matrix of the particle-field system is used to derive the TPL master equation based on Scully-Lamb’s quantum theory of laser. Various dynamical operators of interest for the cavity field are calculated analytically and computed numerically. The sophisticated computational program was developed to …
Growth Of Semi-Polar (11-22) Gan Epitaxial Layer On M-Plane Sapphire Via Mocvd,
2020
Universiti Malaya
Growth Of Semi-Polar (11-22) Gan Epitaxial Layer On M-Plane Sapphire Via Mocvd, Anuar Mohd Afiq
Student Works (2020-2029)
In the past few years, semi-polar (11-22) GaN has attracted much intention in the field of optoelectronics including light-emitting diodes (LEDs), laser diodes (LDs) and photodetectors. Commercially, GaN-based optoelectronic devices are grown along c-plane direction. However, c-oriented GaN-based optoelectronics suffer from piezoelectric polarization, which hinders the device performances. Conversely, semi-polar (11-22) GaN exhibits almost zero piezoelectric polarization effect. Furthermore, as the GaN wurtzite lattice is inclined approximately 58° respective to c-plane, it provides more sites for doping incorporation such as indium, silicon, aluminium, etc. Therefore, the semi-polar (11-22) GaN is presumed to be one of a promising candidate for efficient …
Applications Of Portable Libs For Actinide Analysis,
2020
Air Force Institute of Technology
Applications Of Portable Libs For Actinide Analysis, Ashwin P. Rao, John D. Auxier Ii, Dung Vu, Michael B. Shattan
Faculty Publications
A portable LIBS device was used for rapid elemental impurity analysis of plutonium alloys. This device demonstrates the potential for fast, accurate in-situ chemical analysis and could significantly reduce the fabrication time of plutonium alloys.
Energy Dependent Relative Cross Sections In Carbon 1s Photoionization,
2020
Missouri University of Science and Technology
Energy Dependent Relative Cross Sections In Carbon 1s Photoionization, Michael Schulz, A. Hasan, B. Lamichhane, T. Arthanayaka, M. Dhital, S. Bastola, D. Céolin, C. Nicolas, T. Marchenko, G. Goldsztejn, L. Journel, R. Guillemin, T. X. Carroll, K. J. Børve
Physics Faculty Research & Creative Works
Synopsis We demonstrate that the possibility of monitoring relative photoionization cross sections over a large photon energy range extending to hard x-rays allows studying and disentangling shake processes and intramolecular inelastic scattering effects. An "EXAFS"-type of oscillatory behavior of the relative C 1s cross sections is observed in a wide photon energy range up to 1 keV due to multiple intramolecular elastic scattering of the photoelectron. These effects are also present in solids and constitute a significant part of all elastic and inelastic scattering effects occurring in solids.
