Atomic, Molecular and Optical Physics Commons^™

Equations Of State For Warm Dense Carbon From Quantum Espresso, Derek J. Schauss

Theses and Dissertations

Warm dense plasma is the matter that exists, roughly, in the range of 10,000 to 10,000,000 Kelvin and has solid-like densities, typically between 0.1 and 10 grams per centimeter. Warm dense fluids like hydrogen, helium, and carbon are believed to make up the interiors of many planets, white dwarfs, and other stars in our universe. The existence of warm dense matter (WDM) on Earth, however, is very rare, as it can only be created with high-energy sources like a nuclear explosion. In such an event, theoretical and computational models that accurately predict the response of certain materials are thus very …

Acute Growth Inhibition & Toxicity Analysis Of Nano-Polystyrene Spheres On Raphidocelis Subcapitata, Anthony Reynolds, Michelle Giltrap, Gordon Chambers

Articles

Micro/nano-plastics (MNPs) have been found within many environments and organisms including humans, making them a significant and growing concern. Initial research into the potential detrimental effects these MNPs both from acute and chronic exposure has been ongoing but still requires substantially more data to clarify. This research presents the response of nano-polystyrene (NPS) on Raphidocelis subcapitata, a freshwater alga, under an existing acute toxicity test along with additional analytical techniques to try identifying possible sources of toxicity. R. subcapitata cells were exposed for 72 h to a concentration range of 0–100 mg/l NPS. Growth Inhibition (GI) testing showed the …

Investigating Ice Nucleation At Negative Pressures Using Molecular Dynamics: A First Order Approximation Of The Dependence Of Ice Nucleation Rate On Pressure, Elise Rosky

Dissertations, Master's Theses and Master's Reports

Atmospheric scientists and climate modelers are faced with uncertainty around the process of ice production in clouds. While significant progress has been made in predicting homogeneous and heterogeneous ice nucleation rates as a function of temperature, recent experiments have shown that ice nucleation rates can be enhanced without decreasing temperature, through various mechanical agitations. One hypothesis for these findings is that mechanisms of stretching water and thereby inducing negative pressure in the liquid could lead to an increase in freezing rate. To better understand the viability of this concept, the effect of negative pressure on ice nucleation rates needs to …

Transmission Zeros With Topological Symmetry In Complex Systems, Yuhao Kang, Azriel Genack

Publications and Research

Understanding vanishing transmission in Fano resonances in quantum systems and metamaterials and perfect and ultralow transmission in disordered media, has advanced the understanding and applications of wave interactions. Here we use analytic theory and numerical simulations to understand and control the transmission and transmission time in complex systems by deforming a medium and by adjusting the level of gain or loss. Unlike the zeros of the scattering matrix, the position and motion of the zeros of the determinant of the transmission matrix in the complex plane of frequency and field decay rate have robust topological properties. In systems without loss …

Combining Cryo-Em Density Map And Residue Contact For Protein Secondary Structure Topologies, Maytha Alshammari, Jing He

Computer Science Faculty Publications

Although atomic structures have been determined directly from cryo-EM density maps with high resolutions, current structure determination methods for medium resolution (5 to 10 Å) cryo-EM maps are limited by the availability of structure templates. Secondary structure traces are lines detected from a cryo-EM density map for α-helices and β-strands of a protein. A topology of secondary structures defines the mapping between a set of sequence segments and a set of traces of secondary structures in three-dimensional space. In order to enhance accuracy in ranking secondary structure topologies, we explored a method that combines three sources of information: a set …

Molecular Spectroscopy For Innovative Physics: Alcl & Baf, Alex Preston

Pomona Senior Theses

This thesis is inspired by recent developments in the realm of fundamental physics. Spectroscopic studies on diatomic molecules are at the forefront of such endeavors. High-precision microwave spectroscopy probing the rotational energy level transitions of the molecules AlCl and BaF are analyzed at length in this work. The frequency data for these molecules are evaluated using the programs SPFIT and SPCAT in order to develop a “global fit” numerical model of the rotational, vibrational, nuclear, and hyperfine parameters characterizing the systems. Born-Oppenheimer breakdown terms used to amend inconsistencies in the spectral coefficients are determined for both systems. Previously published data …

Mot-Based Lifetime Measurements Of Potassium-39 5p1/2 And 5p3/2 States, Huan Q. Bui

Honors Theses

This thesis presents measurements of the lifetimes of 5p1/2 and 5p3/2 of K39 via exciting a cloud of K39 atoms in a magneto-optical trap by a linearly-polarized pulse of 405 nm light followed polarization-specific, time-resolved fluorescence detection. We find that $\tau_{5p1/2} = $ 138.8 $\pm$ 1.6 ns, which is consistent with past measurements \cite{triumf}, \cite{berends} and calculations \cite{safranova}. The $\tau_{5p3/2}$ measurement is naturally more involved since quantum beats due to hyperfine and Zeeman effect are present. Our observation of $\tau_{5p3/2} =$ 137.6 $\pm$ 3.1 ns and $\tau_{5p3/2} =$ 136.0 $\pm$ 2.4 ns, obtained from two slightly different approaches, are compared …

Signal-Background Analysis For New Physics At Particle Colliders And The Criteria For Its Discovery, Prudhvi Nikhil Bhattiprolu

Graduate Research Theses & Dissertations

Although the Standard Model (SM) is now complete with the spectacular discovery of the Higgs boson at the Large Hadron Collider (LHC), there are many unsolved puzzles such as the electroweak hierarchy problem, dark matter, neutrino masses, etc., that need to be addressed. Theories proposed to solve these issues often involve new and exotic particles at the TeV scale and beyond. It is therefore of great importance to devise novel strategies to extract new physics signals with small rates lurking in huge backgrounds. My research detailed here is broadly along those lines.

Vectorlike leptons (VLL) are an intriguing possibility for …

Complete Experiments On Multi-Photon Ionizations Of Ultra-Cold And Polarized Atoms, Bishnu Prasad Acharya

Doctoral Dissertations

“Fundamental atomic processes such as collision-induced ionization are of relevance in many scientific fields. Describing these reactions can still pose a substantial challenge due to the well-known “few-body problem”, which entails that there is no analytical solution of the equations of motion for systems of more the 2 mutually interacting particle. Novel experimental tools and advancements in theorical methods enable to obtain detailed information on atomic dynamics providing insight into both, the phase as well as the amplitude of the quantum-mechanical wave functions of the particles. In this project, we developed experimental techniques studying multi-photon ionization of lithium in femto-second …

One-Dimensional Lateral Force Anisotropy At The Atomic Scale In Sliding Single Molecules On A Surface, Yuan Zhang, Daniel J. Trainer, Badri Narayanan, Yang Li, Anh T. Ngo, Sushila Khadka, Arnab Neogi, Brandon Fisher, Larry A. Curtiss, Subramanian K.R.S. Sankaranarayanan, Saw Wai Hla

Physics Faculty Publications

Using a q+ atomic force microscopy at low temperature, a sexiphenyl molecule is slid across an atomically flat Ag(111) surface along the direction parallel to its molecular axis and sideways to the axis. Despite identical contact area and underlying surface geometry, the lateral force required to move the molecule in the direction parallel to its molecular axis is found to be about half of that required to move it sideways. The origin of the lateral force anisotropy observed here is traced to the one-dimensional shape of the molecule, which is further confirmed by molecular dynamics simulations. We also demonstrate that …

Simulating Electron Impact Ionization Using A General Particle Tracer (Gpt) Custom Element, J.T. Yoskowitz, G.A. Krafft, S.B. Van Der Geer, J. Grames, R.M. Soto, C.A.V. Lizarraga

Physics Faculty Publications

A new C++ custom element has been developed with the framework of General Particle Tracer (GPT) to simulate electron impact ionization of residual gas molecules. The custom element uses Monte-Carlo routines to determine both the ion production rate and the secondary electron kinetic energy based on user-defined gas densities and theoretical values for the ionization cross section and the secondary electron differential cross section. It then uses relativistic kinematics to track the secondary electron, the scattered electron, and the newly formed ion after ionization. The ion production rate and the secondary electron energy distribution determined by the custom element have …

Two- And Three-Nucleon Contact Interactions And Ground-State Energies Of Light- And Medium-Mass Nuclei, R. Schiavilla, L. Girlanda, A. Gnech, A. Kievsky, A. Lovato, L. E. Marcucci, M. Piarulli, M. Viviani

Physics Faculty Publications

Classes of two-nucleon (2N) contact interactions are developed in configuration space at leading order (LO), next-to-leading order (NLO), and next-to-next-to-next-to-leading order (N3LO) by fitting the experimental singlet np scattering length and deuteron binding energy at LO, and np and pp scattering data in the laboratory-energy ranges 0–15 MeV at NLO and 0–25 MeV at N3LO. These interactions are regularized by including two Gaussian cutoffs, one for T=0 and the other for T=1 channels. The cutoffs are taken to vary in the ranges R₀=(1.5–2.3) fm and R₁=(1.5–3.0) fm. The 780 (1100) data points up to …

Laser Chirping In Inverse Compton Sources At High Electron Beam Energies And High Laser Intensities, Balŝa Terzić, Jeffrey Mckaig, Erik Johnson, Tabin Dharanikota, Geoffrey A. Krafft

Physics Faculty Publications

The onset of nonlinear effects, such as ponderomotive broadening, increases the radiation bandwidth and thereby places a stringent limitation on the laser intensity used in inverse Compton sources. Recently, we have shown that a judicious longitudinal laser frequency modulation ("chirping") can perfectly compensate for this ponderomotive broadening and restore the narrow band property of scattered radiation in the Thomson regime, when electron recoil during the collision with the laser can be neglected. Consequently, using QED, the laser chirping has been extended to the Compton regime, where electron recoil is properly accounted for. Here we present a new, semiclassical model for …

Environmental Modifications Of Atomic Properties: The Ground And 1s2p Excited States Of Compressed Helium, N. C. Pyper, T. C. Naginey, Colm T. Whelan

Physics Faculty Publications

Atoms remaining as recognizably distinct constituents of bulk condensed phases can have properties modified from those of the isolated species. Dense helium bubbles at high pressures are a common form of radiation damage degrading the mechanical and electrical properties of host materials. Detailed knowledge is critical for predicting their long term performance. Modifications of the ground and first singlet excited states of confined compressed helium are investigated using an entirely non-empirical theory based on the results of ab initio self-consistent field calculations with corrections for the effects of electron correlation. For finite sized portions representing bulk condensed fcc and bcc …