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Full-Text Articles in Physics

Laser Cooling With Adiabatic Transfer On A Raman Transition, Graham Greve, Baochen Wu, James K. Thompson Jul 2019

Laser Cooling With Adiabatic Transfer On A Raman Transition, Graham Greve, Baochen Wu, James K. Thompson

JILA Faculty Contributions

Sawtooth Wave Adiabatic Passage (SWAP) laser cooling was recently demonstrated using a narrow-linewidth single-photon optical transition in atomic strontium and may prove useful for cooling other atoms and molecules. However, many atoms and molecules lack the appropriate narrow optical transition. Here we use such an atom, 87Rb, to demonstrate that two-photon Raman transitions with arbitrarily-tunable linewidths can be used to achieve 1D SWAP cooling without significantly populating the intermediate excited state. Unlike SWAP cooling on a narrow transition, Raman SWAP cooling allows for a final 1D temperature well below the Doppler cooling limit (here, 25 times lower); and the ...


Dispersive Hydrodynamics In Viscous Fluid Conduits, Michelle Maiden Apr 2019

Dispersive Hydrodynamics In Viscous Fluid Conduits, Michelle Maiden

Applied Mathematics Graduate Theses & Dissertations

Viscous fluid conduits provide an ideal system for the study of dissipationless, dispersive hydrodynamics. A dense, viscous fluid serves as the background medium through which a lighter, less viscous fluid buoyantly rises. If the interior fluid is continuously injected, a deformable pipe forms. The long wave interfacial dynamics are well-described by a dispersive nonlinear partial differential equation called the conduit equation.

Experiments, numerics, and asymptotics of the viscous fluid conduit system will be presented. Structures at multiple length scales are characterized, including solitary waves, periodic waves, and dispersive shock waves. A more generic class of large-scale disturbances is also studied ...


Subauroral Neutral Wind Driving And Its Feedback To Saps During The March 17, 2013 Geomagnetic Storm, Banafsheh Ferdousi, Yukitoshi Nishimura, Naomi Maruyama, Larry Lyons Jan 2019

Subauroral Neutral Wind Driving And Its Feedback To Saps During The March 17, 2013 Geomagnetic Storm, Banafsheh Ferdousi, Yukitoshi Nishimura, Naomi Maruyama, Larry Lyons

Cooperative Institute for Research in Environmental Sciences Faculty Contributions

Subauroral Polarization Streams (SAPS) within the dusk-premidnight subauroral sector are associated with closure of region 2 field-aligned current (R2 FAC) through the low conductivity region. Although SAPS have often been studied from a magnetosphere-ionosphere (M-I) coupling perspective, recent observations suggest strong interaction also exists between SAPS and the thermosphere (T). We focuse on thermospheric wind driving and its impact on SAPS and R2 FAC during the March 17, 2013 geomagnetic storm using both observations and the physics-based RCM-CTIPe model that self-consistently couples the M-I-T system. DMSP-18 and GOCE satellite observations show that, as the storm progresses, sunward ion flows intensify ...


A Twist In Strong-Field Physics: Structured, Ultrafast Optical And Extreme Ultraviolet Waveforms With Tailored Spin And Orbital Angular Momentum, Kevin Michael Dorney Jan 2019

A Twist In Strong-Field Physics: Structured, Ultrafast Optical And Extreme Ultraviolet Waveforms With Tailored Spin And Orbital Angular Momentum, Kevin Michael Dorney

Chemistry Graduate Theses & Dissertations

Structured light, which is composed of custom-tailored light waves possessing nontrivial intensity, polarization, and phase, has emerged in recent decades as a powerful tool for probing and controlling light-matter interactions, with wide-reaching applications in fields ranging from microscopy, to scientific/industrial imaging, lithography, and even to forensic science. In particular, structured light possessing optical angular momentum can exhibit both spin and orbital flavors related to the polarization and topological phase structure of light, respectively. This new ability to sculpt light into complex optical patterns has proven to be particularly beneficial for telecommunications, quantum computing, chiral sensing, and super-resolution imaging, to ...


Conformational Dependence Of Σ-Electron Delocalization In The Catenae Xnme2n+2, X = Si, Ge, Sn, And Pb, Milena Jovanovic Jan 2019

Conformational Dependence Of Σ-Electron Delocalization In The Catenae Xnme2n+2, X = Si, Ge, Sn, And Pb, Milena Jovanovic

Chemistry Graduate Theses & Dissertations

Bonds of σ type are the most common chemical bonds, dominating bonding in all molecules and defining the framework of a molecule. It has been long known that electrons in σ bonds can delocalize throughout a molecule. However, the nature of σ-electron delocalization is not fully understood due to its complexity. One of the important aspects of σ-electron delocalization is its conformational dependence, first noted in oligosilanes where properties of a molecule change drastically when it changes conformation. This dissertation describes efforts to understand the conformational dependence of σ delocalization in oligosilanes and their heavier analogs using simple intuitive models ...


Direct Numerical Simulations Of The Compressible Low Atwood Rayleigh-Taylor Instability, Scott A. Wieland Jan 2019

Direct Numerical Simulations Of The Compressible Low Atwood Rayleigh-Taylor Instability, Scott A. Wieland

Mechanical Engineering Graduate Theses & Dissertations

Two fluids are considered Rayleigh-Taylor unstable when the more dense fluid is suspended above the less dense fluid in the presence of a gravitational like accelerative force. When a pertur- bation is applied to the interface between the two, they begin mixing as the light fluid rises and the heavy fluid drops. The extension of this to the compressible regime leads to the densities of the fluids to not be constant, but instead the molar mass is used to define the weights. At the interface, a density jump still occurs, but away from the interface the densities can vary in ...


Thermal Conductivity Of Complex Crystals, High Temperature Materials And Two Dimensional Layered Materials, Xin Qian Jan 2019

Thermal Conductivity Of Complex Crystals, High Temperature Materials And Two Dimensional Layered Materials, Xin Qian

Mechanical Engineering Graduate Theses & Dissertations

Thermal conductivity is a critical property for designing novel functional materials for engineering applications. For applications demanding efficient thermal management like power electronics and batteries, thermal conductivity is a key parameter affecting thermal designs, stability and performances of the devices. Thermal conductivity is also the critical material metrics for applications like thermal barrier coatings (TBCs) in gas turbines and thermoelectrics (TE). Therefore, thermal conductivities of various functional materials have been investigated in the past decade, but most of the materials are simple and isotropic crystals at low temperature. This is because the first-principles calculation is limited to simple crystals at ...


Direct Optically Driven Spin-Charge Dynamics Govern The Femtosecond Response Of Ferromagnets, Phoebe Marie Tengdin Jan 2019

Direct Optically Driven Spin-Charge Dynamics Govern The Femtosecond Response Of Ferromagnets, Phoebe Marie Tengdin

Electrical Engineering Graduate Theses & Dissertations

Ferromagnetic materials have strong electron correlations that drive quantum effects and make the physics that describes them extremely challenging. In particular, the electron, spin, and lattice degrees of freedom can interact in surprising ways when driven out of equilibrium by ultrafast laser excitation. In this thesis I uncover several previously unexpected connections between the electronic and spin systems in ferromagnets. Dynamics occur at unexpectedly fast timescales, driven using femtosecond laser excitation pulses. The tools that I use to observe the exceeding fast (10s of femtosecond) dynamics are bursts of extreme ultraviolet light resonant with the M-edge of transition metals and ...


Mechanisms For Fracton Phases, Han Ma Jan 2019

Mechanisms For Fracton Phases, Han Ma

Physics Graduate Theses & Dissertations

Strongly correlated many-body systems provide a platform for novel phases of matter where constituent particles organize themselves in a variety of ways. At low temperature, these particles interact quantum mechanically and generate entanglement building up exotic quantum phases, such as topologcial order, where there can be emergent excitations which cannot be created locally. Such excitations, if gapped, are also called topological excitations.

Fracton is one of such gapped point-like topological excitation in three dimensional system. Different from conventional topological excitation, it is immobile and was firstly discovered in exact solvable models exhibiting fracton topological order. This new order has sub-extensive ...


Precise Measurements Of Few-Body Physics In Ultracold 39k Bose Gas, Roman Chapurin Jan 2019

Precise Measurements Of Few-Body Physics In Ultracold 39k Bose Gas, Roman Chapurin

Physics Graduate Theses & Dissertations

Ultracold atomic gases with tunable interactions offer an ideal platform for studying interacting quantum matter. While the few- and many-body physics are generally complex and intractable, the problem can be greatly simplified in an atomic gas by a controlled separation of relevant length and energy scales. Precise control of experimental parameters, via Feshbach resonances, optical potentials and radio-frequency radiation, enables deterministic measurements of few-body physics, including universal physics and the Efimov effect. In this thesis, I present our recent studies on precisely measuring two- and three-body physics in an ultracold Bose gas. I begin by describing our new apparatus used ...


Understanding And Manipulating The Thermal Conductance Of Sin Membranes In Sub-Kelvin Refrigerators And Sensors, Xiaohang Zhang Jan 2019

Understanding And Manipulating The Thermal Conductance Of Sin Membranes In Sub-Kelvin Refrigerators And Sensors, Xiaohang Zhang

Physics Graduate Theses & Dissertations

In superconducting transition-edge sensors (TES) and superconducting tunnel junction refrigerators, thermal conductance of the silicon nitride membrane is a key design character. Thermal conductance engineering in silicon nitride membrane is still challenging, especially not introducing extra noise to sensors and diminish its mechanical strength.

In this thesis, we introduce our new generation of macroscopic general-purpose refrigerator using superconducting tunnel junction. Using the product of the cooled mass and the temperature reduction as a performance metric, this work is a more than tenfold advance over previous efforts. Based on our model, a better understanding of phonon thermal conductance of silicon nitride ...


Achieving A Large Density Of Hydroxyl Radicals For Cold Collisions, Hao Wu Jan 2019

Achieving A Large Density Of Hydroxyl Radicals For Cold Collisions, Hao Wu

Physics Graduate Theses & Dissertations

Molecular physics has experienced groundbreaking progress in the fields of precision spectroscopy, chemical reaction kinetics, quantum state engineering and many-body physics. In order to better observe these phenomena, there is an insatiable pursuit of larger trapped molecular densities and longer lifetime. In this thesis, several key milestones that we have recently achieved towards these goals for hydroxyl radicals (OH) are reported. First, we discovered an enhanced spin-flip behavior of dipolar molecules due to the existence of dual (electric and magnetic) dipole moments and obtained a better understanding of complex spin-dynamics for both Hund's case (a) and (b) molecules in ...


Investigating And Valuing The Messy Nature Of Learning: Ontological, Epistemological, And Social Aspects Of Student Reasoning In Quantum Mechanics, Jessica Rae Hoehn Jan 2019

Investigating And Valuing The Messy Nature Of Learning: Ontological, Epistemological, And Social Aspects Of Student Reasoning In Quantum Mechanics, Jessica Rae Hoehn

Physics Graduate Theses & Dissertations

Historically, much of physics education research has focused on whether students’ answers are correct or incorrect. This thesis presents a complementary perspective that moves beyond a dichotomous view of learning by valuing the messy, or complicated and varied, nature of students’ reasoning. We do so by investigating three aspects of student reasoning in quantum mechanics (QM)---ontological (pertaining to the nature of entities), epistemological (pertaining to the nature of knowledge or learning), and social (pertaining to collective reasoning). Through focusing on the kinds of reasoning that students are capable of, we value their creativity, identity, and engagement in our educational ...


The Road Less Traveled: Resonant Bose-Einstein Condensates Via A Hyperspherical Lowest-Order Constrained Variational Approach, Michelle Wynne Ching Sze Jan 2019

The Road Less Traveled: Resonant Bose-Einstein Condensates Via A Hyperspherical Lowest-Order Constrained Variational Approach, Michelle Wynne Ching Sze

Physics Graduate Theses & Dissertations

In this work, we study the ground state properties of a system of $N$ harmonically trapped bosons of mass $m$ interacting with two-body contact interactions, from small to large scattering lengths. This is accomplished in a hyperspherical coordinate system that is flexible enough to describe both the overall scale of the gas and two-body correlations. By adapting the lowest-order constrained variational (LOCV) method, we are able to semi-quantitatively attain Bose-Einstein condensate ground state energies even for gases with infinite scattering length. In the large particle number limit, our method provides analytical estimates for the energy per particle $E_0/N \approx ...


Non-Convex Optimization And Applications To Bilinear Programming And Super-Resolution Imaging, Jessica Gronski Jan 2019

Non-Convex Optimization And Applications To Bilinear Programming And Super-Resolution Imaging, Jessica Gronski

Applied Mathematics Graduate Theses & Dissertations

Bilinear programs and Phase Retrieval are two instances of nonconvex problems that arise in engineering and physical applications, and both occur with their fundamental difficulties. In this thesis, we consider various methods and algorithms for tackling these challenging problems and discuss their effectiveness.

Bilinear programs (BLPs) are ubiquitous in engineering applications, economics, and operations research, and have a natural encoding to quadratic programs. They appear in the study of Lyapunov functions used to deduce the stability of solutions to differential equations describing dynamical systems. For multivariate dynamical systems, the problem formulation for computing an appropriate Lyapunov function is a BLP ...


Multi-Object-Plane Phase Retrieval For Plasma Density Profile Reconstruction, Xiang Chen Jan 2019

Multi-Object-Plane Phase Retrieval For Plasma Density Profile Reconstruction, Xiang Chen

Undergraduate Honors Theses

Plasma Wakefield Accelerators (PWFA) can accelerate electron beams with gradients that are hundreds of times greater than conventional RF accelerators and may provide a path toward a future energy frontier lepton collider. The ability to preserve the beam emittance depends strongly on the longitudinal density profile of the PWFA plasma source. One method of generating the plasma source is to ionize a gas such as argon or helium with a high intensity laser pulse. This plasma source quickly recombines on the order of nanoseconds, and so a new plasma source must be created for every shot. The plasma source is ...


Measurement Of Pwfa Plasma Source Density Using Stark Broadening, Shao Lee Jan 2019

Measurement Of Pwfa Plasma Source Density Using Stark Broadening, Shao Lee

Undergraduate Honors Theses

The Plasma Wakefield Accelerator (PWFA) is a type of advanced particle accelerator that can generate high energy particle beams with a reduced footprint and cost compared to conventional accelerators. Recent experiments have shown that the PWFA is able to accelerate an electron beam by 9 GeV in just over a meter. However, to continue making progress the PWFA must be shown to also preserve the beam quality, as quantified by the beam emittance. This requires a carefully tailored plasma source, and therefore, a sufficiently reliable plasma density diagnostic. Stark broadening has been frequently used as a laboratory plasma diagnostic as ...


Systematic Exploration Of The Inverse Cascade In Rapidly Rotating Convection, Mitchell Krouss Jan 2019

Systematic Exploration Of The Inverse Cascade In Rapidly Rotating Convection, Mitchell Krouss

Undergraduate Honors Theses

A detailed investigation of the formation of large-scale vortices (LSVs) in rapidly rotating convection is carried out with an asymptotically-reduced model. The LSVs are generated by an inverse cascade of kinetic energy, which transfers kinetic energy from small length scales to large length scales. We can identify parameters, describing fluids, containing the presence of an inverse cascade by evaluating the transfer of kinetic energy to different wave numbers. We find a critical vertical Reynolds number that delineates the transition to flows which show a robust inverse cascade. The vertical Reynolds number can be fit with a multi-parameter power law, which ...


Direct Photon Identification In Heavy Ion Collisions At Sphenix, Chase Smith Jan 2019

Direct Photon Identification In Heavy Ion Collisions At Sphenix, Chase Smith

Undergraduate Honors Theses

The sPHENIX experiment at Brookhaven National Laboratory’s Relativistic Heavy Ion Collider (RHIC) will be a new detector with the purpose of studying the strongly interacting matter created in high energy Au+Au collisions. The high energy den- sity created in Au+Au collisions produces a medium of disassociated quarks and gluons called Quark Gluon Plasma (QGP), which is the same substance which ex- isted in the first microsecond of the universe. As a result of its incredibly strong interactions QGP is difficult to study; however, using the phenomena of jet quench- ing with photon jet pairs it is possible ...


Non-Reciprocity In An Active Two-Dimensional Lattice Circuit, Justin White Jan 2019

Non-Reciprocity In An Active Two-Dimensional Lattice Circuit, Justin White

Undergraduate Honors Theses

Circulators are crucial components in quantum computers that ensure that quantum information is coherently transported. Current commercial circula- tors are too bulky because they use permanent magnets, so producing chip- scale circulators is necessary to feasibly scale up the size of quantum computers using superconducting qubits. Using a model inspired by a paper by Rudner [2], I have designed a lattice circuit that will produce non-reciprocity, which is the property required for proper circulation. These lattice circuits are able to produce circulation because they have periodically time-dependent bonds that control interactions between the sites in the lattice. In this thesis ...


Kinematics Of Tau Lepton Decays, Aidan Bohenick Jan 2019

Kinematics Of Tau Lepton Decays, Aidan Bohenick

Undergraduate Honors Theses

In particle physics, when a particle decays, it is not always possible to fully reconstruct the decaying particle. This is due to the nature that some particles, such as neutrinos, do not typically interact and go straight through the detector unnoticed. This means when attempting to reconstruct the original mass of the decay, there will be missing information. Thus, the question is, even when there is missing information in a decay, is it possible to accurately reconstruct the decaying particle? In this project we will be focusing on the decay of Z->TauhTauh, which will henceforth be ...


Automated Motion Of A Radiation Source For Testing Micromegas Detectors & Modeling Qgp Flow Coefficients Using A Particle Transport Model, Karoline Dapprich Jan 2019

Automated Motion Of A Radiation Source For Testing Micromegas Detectors & Modeling Qgp Flow Coefficients Using A Particle Transport Model, Karoline Dapprich

Undergraduate Honors Theses

This thesis consists of two independent parts. In the first section, an automated system for moving a radiation source for testing micromegas detectors was designed, assembled, and programmed. Micromegas amplify the signal from incident radiation through the ionization of the gas filling the detectors. They are reliable and maintain high accuracy under high incident particle flux conditions, but remain vulnerable to ion backflow, which reduces tracking accuracy. To characterize ion backflow, the current drawn by the detector's drift mesh can be measured. However, due to the current's picoamp scale it is very sensitive to noise and drift, which ...


Ac Susceptometry For Characterizing Magnetic Spin Structures, Mark Maus Jan 2019

Ac Susceptometry For Characterizing Magnetic Spin Structures, Mark Maus

Undergraduate Honors Theses

Magnetic phase transitions between non-trivial ordered states are investigated through AC Susceptibility measurements. An AC Susceptometer was built for the purpose of detecting variations in a material’s magnetic structure in response to adjustments of external conditions. The AC Susceptometer is sensitive to subtle changes in magnetic ordering, indicated by distinct features in measured AC Susceptibility data when a phase transition occurs. The coil design and characterization is discussed in detail. The dependence of AC Susceptibility on temperature and applied DC field conditions are explored in samples of Cr1/3NbS2, 10% Iron-doped MnSi (Mn0.9Fe ...


Rempd Spectroscopy Of Thf+ And A Modular Delayed Self-Heterodyne Interferometer, Kevin Boyce Jan 2019

Rempd Spectroscopy Of Thf+ And A Modular Delayed Self-Heterodyne Interferometer, Kevin Boyce

Undergraduate Honors Theses

The JILA eEDM project currently seeks to improve its sensitivity to the electron’s permanent electric dipole moment, a quantity of fundamental importance to new extensions to the Standard Model, using tabletop experimental techniques familiar to atomic, molecular, and optical physics. The current generation of the experiment uses HfF+ polarized molecular ions trapped in a rotating electric bias field to measure the Stark shift on a particular pair of hyperfine states due to this permanent dipole moment. However, a future generation of the experiment hopes to perform the measurement in a different species, ThF+, due to its intrinsically stronger interatomic ...


Local Holographic Superconductors And Hovering Black Holes, Atakan Hilmi Firat Jan 2019

Local Holographic Superconductors And Hovering Black Holes, Atakan Hilmi Firat

Undergraduate Honors Theses

Understanding the behavior of the high-Tc superconductors is among the most important open questions in physics where many conventional field theoretical methods fail due to strong interactions of electrons. Recent advancements in string theory and holographic dualities that map d+1 dimensional quantum field theories in strongly coupled regimes to d+2 dimensional weakly curved classical general relativity proved to be useful for understanding the high-Tc superconductivity behavior. It is shown that the general properties of so-called holographic superconductors of the field theory side can be extracted by investigating the hair of the charged scalar field around the black hole ...


The Magnetic Fields And Their Noise In The Next Generation Ultracold Strontium Optical Lattice Clock, Jacob Scott Jan 2019

The Magnetic Fields And Their Noise In The Next Generation Ultracold Strontium Optical Lattice Clock, Jacob Scott

Undergraduate Honors Theses

The first generation Ultracold Strontium Optical Lattice Clock has achieved an uncertainty on the order of 10^-18 using a 1D optical lattice. The next generation clock is now being constructed with the goal of achieving uncertainties on the 10^-19 level. To achieve this goal, the system will be upgraded to a 3D optical lattice and new apparatus is being built with lower noise and better compatibility with this new system. This thesis discusses the design and construction of the current driving system for the magnetic fields in the experiment. It also presents the design, construction, and testing of ...


Numerical Simulations Of Convection With A Horizontal Magnetic Field, Talal Al-Refae Jan 2019

Numerical Simulations Of Convection With A Horizontal Magnetic Field, Talal Al-Refae

Undergraduate Honors Theses

A numerical study of magnetoconvection with a horizontal magnetic field in a plane layer geometry is conducted. Novel dynamical regimes are observed beyond those occurring in classical (i.e non-magnetic) Rayleigh-Bénard convection. Imposed magnetic field strengths up to Chandrasekhar numbers of Q = 106 are investigated. The most unstable flow configuration is two-dimensional rolls oriented parallel to the direction of the imposed magnetic field in which the induced magnetic field is identically zero. The convective roll structure exhibits a preferential flow alignment along the direction of the imposed magnetic field thereby sustaining an anisotropic flow field. Deviations away from the ...


Optimizing Association Of Heteronuclear Feshbach Molecules In Microgravity With A Magnetic Field Quench, Kirk Waiblinger Jan 2019

Optimizing Association Of Heteronuclear Feshbach Molecules In Microgravity With A Magnetic Field Quench, Kirk Waiblinger

Undergraduate Honors Theses

This work presents a computational comparison of two magnetic field manipulation schemes for creating heteronuclear 87Rb41K Feshbach molecules. We focus on analysis of the parameters relevant to the NASA Cold Atom Laboratory experiments performing atom interferometry, which will require maximizing production of molecules at low densities, and extremely low temperatures (<1 nK). It is found that a scheme involving a magnetic field quench potentially offers substantial benefits over a direct linear magnetic field sweep across a Feshbach resonance.


Infrared Vibrational Spectroscopy Of Cold Hydrocarbons, David Welsh Jan 2019

Infrared Vibrational Spectroscopy Of Cold Hydrocarbons, David Welsh

Undergraduate Honors Theses

Infrared vibrational spectroscopy is a tool commonly used by physicists and chemists to study and identify chemical compounds. It exploits the fact that a molecule may absorb electromagnetic radiation that is characteristic to its structure, causing the bonds to stretch is some manner. This quantum mechanical phenomenon can be mathematically modeled, giving physicists a method to predict where these absorptions can occur. Vibrational spectroscopy can be used in conjunction with a buffer-gas molecular beam to create a cold, isolated matrix of inert molecules to trap a molecule of interest. Cold trapping a molecule in this manner, using a buffer gas ...


Hydrodynamics Of Smectic Liquid Crystal Films, Eric Minor Jan 2019

Hydrodynamics Of Smectic Liquid Crystal Films, Eric Minor

Undergraduate Honors Theses

Smectic A and C liquid crystals are capable of forming incredibly thin films, discretized by the number of molecular layers. This property makes liquid crystal films ideal for studying 2D hydrodynamics, a field of great interest both due to its fundamental importance to physics and because of its applications to biological systems. The phospholipid bilayer which makes up cell membranes is itself an ideal 2D fluid as it consists of only two layers of phospholipids, however cell membranes are incredibly small and difficult to work worth. Liquid crystal films can be several millimeters across and stable for long periods of ...