Atomic, Molecular and Optical Physics Commons^™

Theoretical Calculations For Electron Impact Ionization Of Atoms And Molecules, Sadek Mohamed Fituri Amami

Doctoral Dissertations

"In the last twenty years, significant progress has been made for the theoretical treatment of electron impact ionization (e,2e) of atoms and molecules and, for some cases, very nice agreement between experiment and theory has been achieved. In particular, excellent agreement between theory and experiment and theory has been achieved for ionization of hydrogen and helium. However, agreement between experiment and theory is not nearly as good for ionization of larger atoms and molecules. In the first part of this dissertation, different theoretical approaches will be employed to study the triply differential cross section (TDCS) for low and intermediate energy …

Ruo2 Ph Sensor With Super-Glue-Inspired Reference Electrode, Wade Lonsdale, Magdalena Wajrak, Kamal Alameh

Research outputs 2014 to 2021

A pH-sensitive RuO2 electrode coated in a commercial cyanoacrylate adhesive typically exhibits very low pH sensitivity, and could be paired with a RuO2 working electrode as a differential type pH sensor. However, such sensors display poor performance in real sample matrices. A pH sensor employing a RuO2 pH-sensitive working electrode and a SiO2-PVB junction-modified RuO2 reference electrode is developed as an alternative high-performance solution. This sensor exhibits a performance similar to that of a commercial glass pH sensor in some common sample matrices, particularly, an excellent pH sensitivity of 55.7 mV/pH, a hysteresis as low as 2.7 mV, and a …

Orbital Stability Results For Soliton Solutions To Nonlinear Schrödinger Equations With External Potentials, Joseph B. Lindgren

Theses and Dissertations--Mathematics

For certain nonlinear Schroedinger equations there exist solutions which are called solitary waves. Addition of a potential $V$ changes the dynamics, but for small enough $||V||_{L^\infty}$ we can still obtain stability (and approximately Newtonian motion of the solitary wave's center of mass) for soliton-like solutions up to a finite time that depends on the size and scale of the potential $V$. Our method is an adaptation of the well-known Lyapunov method.

For the sake of completeness, we also prove long-time stability of traveling solitons in the case $V=0$.

Magnetic Behavior Of Bulk And Nanostructured Mnxtas2, Lucas Paul Beving

Honors Program Theses

At its base, material science research aims to categorize specific materials by their various attributes, such as structure, integrity, electronic properties, magnetic properties, and others. By categorizing materials in this way, it becomes easier to generalize the application of a specific material to those within a broader category. The interest in materials that exhibit useful characteristics at small scales derives directly from the technology industry’s need for smaller and smaller devices. Two-dimensional materials are of great interest for this reason.

Two-dimensional materials are comprised of many single layers, or planes, stacked together to create a crystal. Each layer may be …

Dualism Between Optical And Difference Parametric Amplification, Wayne Cheng-Wei Huang, Herman Batelaan

Department of Physics and Astronomy: Faculty Publications

Breaking the symmetry in a coupled wave system can result in unusual amplification behavior. In the case of difference parametric amplification the resonant pump frequency is equal to the difference, instead of the sum, frequency of the normal modes. We show that sign reversal in the symmetry relation of parametric coupling give rise to difference parametric amplification as a dual of optical parametric amplification. For optical systems, our result can potentially be used for efficient XUV amplification.

Comment On “Electronic Structure Of Mo(1−X)Rex Alloys Studied Through Resonant Photoemission Spectroscopy”, Prescott Evans, Peter A. Dowben

Peter Dowben Publications

Further analysis of the resonant photoemission data, found within Sundar et al (2016 J. Phys.: Condens. Matter 28 315502), show the intensities do not follow the elemental composition in the Mo_1−xRe_x alloy. Similar trends are observed in the published data for Gd_1−xNi_x alloy films. The analysis of the resonant photoemission intensities suggests that Mo in the Mo_1−xRe_x alloy and Gd in the Gd_1−xNi_x alloy have nearest neighbor bonds to Re and Ni respectively. This means the A–B bond is favored over the average of …

Nature Of Bonding In Bimetallic Or Ligated Aluminum Clusters, Cam J. Grover

Theses and Dissertations

In this study, Amsterdam Density Functional software is used to model bimetallic and ligated aluminum clusters. The stability of the bimetallic clusters is well described by the Jellium model, and the nature of bonding between dopants and aluminum in the bimetallic clusters is analyzed using different criteria. We find that sodium tends to bind ionically, while the bonding of magnesium is not so obvious. We also determine that examining the Mulliken population is the most useful parameter in differentiating bonding character. Calculations on ligated aluminum clusters reveal it behaves fundamentally different than the bimetallic clusters studied in the first part. …

Investigations Into Structure And Properties Of Atomically-Precise Transition Metal-Chalcogenide Clusters Of Crte And Ligated Cr6te8(Pet3)6, Anthony F. Pedicini

Theses and Dissertations

The complete understanding of a clusters electronic structure, the primary mechanisms for its properties and stabilization is necessary in order to functionalize them for use as building blocks within novel materials. First principle theoretical studies have been carried out upon the electronic properties of Cr_xTe_y (x = 1 – 6, y = 0 – 8, x + y ≤ 14), as well as for the larger triethylphosphine (PEt₃) ligated cluster system of Cr₆Te₈(PEt₃)₆. Together, we aim to use the information garnered from the smaller clusters to address …

Development And Characterisation Of A Bath-Based Vertical Blackbody Cavity Calibration Source For The Range −30 °C To 150 °C, Sam Boles, Igor Pušnik, Dubhaltach Mac Lochlainn, David Fleming, Izabela Naydenova, Suzanne Martin

Articles

Industrial use of Radiation Thermometers (RTs) is becoming increasingly common due to the perceived advantages and wide market availability. Blackbody Cavity Radiation Sources (BCRSs) are typically used for calibration of these instruments, and these cavities are oriented horizontally in most cases. For BCRSs based in thermal baths, this necessitates the use of custom-built baths with side openings. This paper presents a unique design of vertical bath-based BCRS that may be immersed in conventional calibration baths without modifications to the baths. The method, results, and analysis of an international comparison comparing this vertical BCRS, standard horizontal BCRSs, and a previous iteration …

Transverse Parton Momenta In Single Inclusive Hadron Production In E+E- Annihilation Process., M. Boglione, J. O. Gonzalez-Hernandez, R. Taghavi

Physics Faculty Publications

We study the transverse momentum distributions of single inclusive hadron production in e⁺e⁻ annihilation processes. Although the only available experimental data are scarce and quite old, we find that the fundamental features of transverse momentum dependent (TMD) evolution, historically addressed in Drell–Yan processes and, more recently, in Semi-inclusive deep inelastic scattering processes, are visible in e⁺e⁻ annihilations as well. Interesting effects related to its non-perturbative regime can be observed.

We test two different parameterizations for the p⊥ dependence of the cross section: the usual Gaussian distribution and a power-law model. We find the latter …

Coincidence Charged-Current Neutrino-Induced Deuteron Disintegration For 2H216O, J. W. Van Orden, T. W. Donnelly, O. Moreno

Physics Faculty Publications

Semi-inclusive charge-changing neutrino reactions on targets of heavy water are investigated with the goal of determining the relative contributions to the total cross section of deuterium and oxygen in kinematics chosen to emphasize the former. The study is undertaken for conditions where the typical neutrino beam energies are in the few GeV region, and hence relativistic modeling is essential. For this, the previous relativistic approach for the deuteron is employed, together with a spectral function approach for the case of oxygen. Upon optimizing the kinematics of the final-state particles assumed to be detected (typically a muon and a proton) it …

Moving Towards The Magnetoelectric Graphene Transistor, Shi Cao, Zhiyong Xiao, Chun Pui Kwan, Kai Zhang, Jonathan P. Bird, Lu Wang, Wai-Ning Mei, Xia Hong, Peter A. Dowben

Xia Hong Publications

The interfacial charge transfer between mechanically exfoliated few-layer graphene and Cr₂O₃ (0001) surfaces has been investigated. Electrostatic force microscopy and Kelvin probe force microscopy studies point to hole doping of few-layer graphene, with up to a 150 meV shift in the Fermi level, an aspect that is confirmed by Raman spectroscopy. Density functional theory calculations furthermore confirm the p-type nature of the graphene/chromia interface and suggest that the chromia is able to induce a significant carrier spin polarization in the graphene layer. A large magnetoelectrically controlled magneto-resistance can therefore be anticipated in transistor structures based on this …

Ch3Nh3Pbi3 Perovskites: Ferroelasticity Revealed, Evgheni Strelcov, Qingfeng Dong, Tao Li, Jungseok Chae, Yuchuan Shao, Yehao Deng, Alexei Gruverman, Jinsong Huang, Andrea Centrone

Alexei Gruverman Publications

Ferroelectricity has been proposed as a plausible mechanism to explain the high photovoltaic conversion efficiency in organic-inorganic perovskites; however, convincing experimental evidence in support of this hypothesis is still missing. Identifying and distinguishing ferroelectricity from other properties, such as piezoelectricity, ferroelasticity, etc., is typically nontrivial because these phenomena can coexist in many materials. In this work, a combination of microscopic and nanoscale techniques provides solid evidence for the existence of ferroelastic domains in both CH₃NH₃PbI₃ polycrystalline films and single crystals in the pristine state and under applied stress. Experiments show that the configuration of CH …

Anomalous Photovoltaic Effect In Organic-Inorganic Hybrid Perovskite Solar Cells, Yongbo Yuan, Tao Li, Qi Wang, Jie Xing, Alexei Gruverman, Jinsong Huang

Alexei Gruverman Publications

Organic-inorganic hybrid perovskites (OIHPs) have been demonstrated to be highly successful photovoltaic materials yielding very-high-efficiency solar cells. We report the room temperature observation of an anomalous photovoltaic (APV) effect in lateral structure OIHP devices manifested by the device’s open-circuit voltage (V_OC) that is much larger than the bandgap of OIHPs. The persistent V_OC is proportional to the electrode spacing, resembling that of ferroelectric photovoltaic devices. However, the APV effect in OIHP devices is not caused by ferroelectricity. The APV effect can be explained by the formation of tunneling junctions randomly dispersed in the polycrystalline films, which allows …

Domain Formation Mechanism Of The Si(110) “16 × 2” Reconstruction, N. K. Lewis, Nathan B. Clayburn, Evan M. Brunkow, Timothy J. Gay, Y. Lassailly, J. Fujii, I. Vobornik, W. R. Flavell, E. A. Seddon

Timothy J. Gay Publications

The main factor that determines which of the two domains forms upon reconstruction of the Si(110) “16 × 2” surface has been investigated. Low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) images showed that the domain orientation was independent of the heating current direction used to induce the Si(110) “16 × 2” reconstruction. Reciprocal-space lattice models of the reconstruction allowed for the correct identification of domain orientations in the LEED images, and they confirmed that the reconstruction is two dimensionally chiral. It is proposed that the domain orientation upon surface reconstruction is determined by the direction of monatomic steps …

Structure Evolution And Multiferroic Properties In Cobalt Doped Bi4Ndti3Fe1-XCoXO15- Bi3Ndti2Fe1-XCoxo12-Δ Intergrowth Aurivillius Compounds, D. L. Zhang, W. C. Huang, Z. W. Chen, W. B. Zhao, L. Feng, M. Li, Y. W. Yin, S. N. Dong, X. G. Li

Department of Physics and Astronomy: Faculty Publications

Here, we report the structure evolution, magnetic and ferroelectric properties in Co-doped 4- and 3-layered intergrowth Aurivillius compounds Bi₄NdTi₃Fe_1-x Co_xO₁₅-Bi₃NdTi₂Fe_1-xCo_xO_12-δ. The compounds suffer a structure evolution from the parent 4-layered phase (Bi₄NdTi₃FeO₁₅) to 3-layered phase (Bi₃NdTi₂CoO_12-δ) with increasing cobalt doping level from 0 to 1. Meanwhile the remanent magnetization and polarization show opposite variation tendencies against the doping level, and the sample with x = …

Radiation Therapy Medical Physics Review – Delivery, Interactions, Safety, Feasibility, And Head To Head Comparisons Of The Leading Radiation Therapy Techniques, Cielle Collins

Honors Theses and Capstones

Radiation therapy uses high energy radiation to kill cancer cells. Radiation therapy for cancer treatment can take the form of photon therapy (using x-rays and gamma rays), or charged particle therapy including proton therapy and electron therapy. Within these categories, numerous methods of delivery have been developed. For example, a certain type of radiation can be administered by a machine outside of the body, called external-beam radiation therapy, or by a “seed” placed inside of the body near cancer cells, called internal radiation therapy or brachytherapy. Approximately half of all cancer patients receive radiation therapy, and the form of radiation …

Schrödinger Theory Of Electrons In Electromagnetic Fields: New Perspectives, Viraht Sahni, Xiao-Yin Pan

Publications and Research

The Schrödinger theory of electrons in an external electromagnetic field is described from the new perspective of the individual electron. The perspective is arrived at via the time-dependent "Quantal Newtonian" law (or differential virial theorem). (The time-independent law, a special case, provides a similar description of stationary-state theory). These laws are in terms of "classical" fields whose sources are quantal expectations of Hermitian operators taken with respect to the wave function. The laws reveal the following physics: (a) in addition to the external field, each electron experiences an internal field whose components are representative of a specific property of the …

Electron Correlations In An Excited State Of A Quantum Dot In A Uniform Magnetic Field, Marlina Slamet, Viraht Sahni

Publications and Research

Electron correlations in a two-electron two-dimensional ‘artificial atom’ or quantum dot (with harmonic confining potential) in the presence of a uniform magnetic field in an excited singlet state are studied via quantal density functional theory (QDFT). QDFT allows for the separation of the electron correlations due to the Pauli exclusion principle and Coulomb repulsion, as well as the determination of the contribution of these correlations to the kinetic energy. The QDFT mapping is from the excited state of the quantum dot to one of noninteracting fermions in their ground state possessing the same basic variables of the density and physical …

Generalization Of The Schrödinger Theory Of Electrons, Viraht Sahni

Publications and Research

The Schrödinger theory for a system of electrons in the presence of both a static and time-dependent electromagnetic field is generalized so as to exhibit the intrinsic self-consistent nature of the corresponding Schrödinger equations. This is accomplished by proving that the Hamiltonian in the stationary-state and time-dependent cases {\hat{H}; \hat{H}(t)} are exactly known functionals of the corresponding wave functions {\Psi; \Psi(t)}, i.e. \hat{H} = \hat{H}[\Psi] and \hat{H}(t) = \hat{H}[\Psi(t)]. Thus, the Schrödinger equations may be written as \hat{H}[\Psi]\Psi = E[\Psi]\Psi and \hat{H}[\Psi(t)]\Psi(t) = i\partial\Psi(t)/\partial t. As a consequence the eiegenfunctions and energy eigenvalues {\Psi; E} of the stationary-state equation, and …