Dissertations / Theses on the topic 'Atomic physics'

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1

Del, Punta Jessica A. "Mathematical methods in atomic physics." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0035/document.

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Les problèmes de diffusion de particules, à deux et à trois corps, ont une importance cruciale en physique atomique, car ils servent à décrire différents processus de collisions. Actuellement, le cas de deux corps peut être résolu avec une précision numérique désirée. Les problèmes de diffusion à trois particules chargées sont connus pour être bien plus difficiles mais une déclaration similaire peut être affirmée. L’objectif de ce travail est de contribuer, d’un point de vue analytique, à la compréhension des processus de diffusion Coulombiens à trois corps. Ceci a non seulement un intérêt fondamental, mais est également utile pour mieux maîtriser les approches numériques en cours d’élaboration au sein de la communauté de collisions atomiques. Pour atteindre cet objectif, nous proposons d’approcher la solution du problème avec des développements en séries sur des ensembles de fonctions appropriées et possédant une expression analytique. Nous avons ainsi développé un nombre d’outils mathématiques faisant intervenir des fonctions Coulombiennes, des équations différentielles de second ordre homogènes et non-homogènes, et des fonctions hypergéométriques à une et à deux variables
Two and three-body scattering problems are of crucial relevance in atomic physics as they allow to describe different atomic collision processes. Nowadays, the two-body cases can be solved with any degree of numerical accuracy. Scattering problem involving three charged particles are notoriously difficult but something similar -- though to a lesser extent -- can be stated. The aim of this work is to contribute to the understanding of three-body Coulomb scattering problems from an analytical point of view. This is not only of fundamental interest, it is also useful to better master numerical approaches that are being developed within the collision community. To achieve this aim we propose to approximate scattering solutions with expansions on sets of appropriate functions having closed form. In so doing, we develop a number of related mathematical tools involving Coulomb functions, homogeneous and non-homogeneous second order differential equations, and hypergeometric functions in one and two variables
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2

Bailey, Stephen Malcolm William. "Relativistic atomic photoionization." Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387976.

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3

Radev, Rossen. "Monte Carlo Group - Atomic Physics Department." Phd thesis, Monte Carlo Group, Atomic Physics Department, University of Sofia, 1997. http://cluster.phys.uni-sofia.bg:8080/.

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4

McAlinden, Mary Trea. "Atomic collisions involving positrons." Thesis, Queen's University Belfast, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317480.

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5

O'Connor, Daryl John. "Atomic collisions with surfaces." Thesis, Canberra, ACT : The Australian National University, 1997. http://hdl.handle.net/1885/144473.

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6

Hutzler, Nicholas Richard. "A New Limit on the Electron Electric Dipole Moment| Beam Production, Data Interpretation, and Systematics." Thesis, Harvard University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3626724.

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The charge distribution associated with an electron has surprising implications for a number of outstanding mysteries in physics. Why is the universe made out of matter versus anti-matter, instead of both equally? What new particles and interactions lie beyond the current reach of accelerators like the LHC? Models which propose answers to these questions, such as Supersymmetry, tend to predict a small, yet potentially measurable, asymmetric interaction between an electron and an electric field, characterized by an electric dipole moment (EDM). Despite over six decades of experimental searching, no EDM of any fundamental particle has ever been measured; however, these experiments continue to provide some of the most stringent limits on new physics. Here, we present the results of a new search for the electron EDM, de = (-2.1 ± 3.7stat ± 2.5syst) × 10-29 e cm, which represents an order of magnitude improvement in sensitivity from the previous best limit. Since our measurement is consistent with zero, we present the upper limit of |de| < 8.7 × 10-29 e cm with 90 percent confidence.

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7

Plimmer, Mark David. "Laser spectroscopy of atomic systems." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329991.

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8

Thomas, Malcolm. "Electron scattering by atomic oxygen." Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337031.

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9

Harris, M. "Collisional effects in atomic spectra." Thesis, University of Newcastle Upon Tyne, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.352727.

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10

Hromada, Ivan Jr. "Measurements of Atomic Beam Velocities with Phase Choppers and Precision Measurements of Alkali Atomic Polarizabilities." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/318837.

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Atom interferometers, in which de Broglie waves are coherently split and recombined to make interference fringes, now serve as precision measurement tools for several quantities in physics. Examples include measurements of Newton's constant, the fine structure constant, van der Waals potentials, and atomic polarizabilities. To make next-generation measurements of static electric dipole atomic polarizabilities with an atom beam interferometer, I worked on new methods to precisely measure the velocity distribution for atom beams. I will explain how I developed and used phase choppers to measure lithium, sodium, potassium, and cesium atomic beam velocities with 0.07% accuracy. I also present new measurements of polarizability for these atoms. I classify systematic errors into two broad categories: (1) fractional errors that are similar for all different types of atoms in our experiments, and (2), errors that scale with de Broglie wavelength or inverse atomic momentum in our experiments. This distinction is important for estimating the uncertainty in our measurements of ratios of atomic polarizabilities, e.g., αCs / αNₐ = 2.488(12).
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11

Vrinceanu, Daniel. "Quantal-classical correspondence in atomic collisions." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/28035.

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12

Ruprecht, Peter Andrew. "Time-dependent studies of atomic systems." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308703.

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13

Woodman, George Henry. "Precise laser spectroscopy of atomic hydrogen." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316894.

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14

Sawey, Partick Martin Joseph. "Large scale atomic R-matrix calculations." Thesis, Queen's University Belfast, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356860.

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15

Diaz, Daniel Cipriano. "Threshold resonances in atomic three-body systems." Thesis, California State University, Long Beach, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10142970.

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Atomic resonances present a difficult chapter in the study of atomic structure. The calculation and measurement of these resonant states have provided a challenge for both theorists and experimentalists. This work focuses on the numerical calculation of the resonant states. Some years ago a method to calculate the resonant states of three-body atomic interactions was developed. This method involves solving the Faddeev equations using a Merkuriev cut and a Coulomb-Sturmian basis, and will be the method used for the calculations in this work. This method was used as an alternative to the more conventional methods of calculating atomic resonant states. At the time of its derivation, the method was used to calculate the narrow-width resonances of the electron-Positronium (e – Ps) system, which showed accurate results with respect to the calculations done by other groups using alternative methods. Additionally, the method saw an emergence of resonances (broad-width) which line-up to the system thresholds. We have come to call these broad-width resonances the threshold resonances. However, at the time, these threshold resonances proved too computationally intensive to make confident results. Now, with the assistance of better computational resources and an improved code, this problem is again addressed.

New calculations of the narrow-width and threshold resonances were completed which support the appearance of the threshold resonances in the e – Ps system. The threshold resonances were observed lining up at the first, second, and third two-body thresholds, a trend that is assumed to continue at even higher energies. Calculations were carried out for both the 1S and 3S states. After successfully making calculations of the e – Ps system resonant states, calculations were also carried out for the electron-Hydrogen (e–H) 1S and 3S resonances. The calculations for the e – H system were carried out for the threshold resonances emerging from the 1st threshold. Additionally, we propose an explanation for the emergence of the threshold resonances.

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16

Henkel, Carsten, Andrew M. Steane, Robin Kaiser, and Jean Dalibard. "A modulated mirror for atomic interferometry." Universität Potsdam, 1994. http://opus.kobv.de/ubp/volltexte/2010/4227/.

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A novel atomic beam splitter, using reflection of atoms off an evanescent light wave, is investigated theoretically. The intensity or frequency of the light is modulated in order to create sidebands on the reflected de Broglie wave. The weights and phases of the various sidevands are calculated using three different approaches: the Born approximation, a semiclassical path integral approach, and a numerical solution of the time-dependent Schrdinger equation. We show how this modulated mirror could be used to build practical atomic interferometers.
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17

Van, Camp Mackenzie A. (Mackenzie Anne). "Towards a high-precision atomic gyroscope." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/83772.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 69-72).
In this thesis, I report on the design and construction of the Rubidium Atomic Gyroscope Experiment (RAGE) at Draper Lab.
by Mackenzie A. Van Camp.
S.M.
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18

Fried, Dale G. (Dale George) 1968. "Bose-Einstein condensation of atomic hydrogen." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/84757.

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19

Bloom, Benjamin Jacob S. B. Massachusetts Institute of Technology. "Atomic quantum memory for photon polarization." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44214.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2008.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (leaves 79-82).
Using an ensemble of ultracold Cesium atoms in an optical cavity we demonstrate the efficient storage and retrieval of quantum information in the form of single photons. We use a photon that has scattered into the cavity mode to herald a successful creation of a collective excitation of Cesium atoms and hence our ability to retrieve a photon from the stored excitation at a later time. Post-selecting out only data that was preceded by a heralding photon we have achieved single-photon recovery efficiencies as high as 84%. We construct an atomic quantum memory for arbitrary optical polarization states using this technique on two spatially overlapped atomic samples. The two samples constitute a quantum memory making use of a bijective mapping between a photon polarization and a shared collective excitation in the atoms. The stored state is later retrieved as a single-photon polarization state. This memory showed an average fidelity of 0.93(5) for the recovered fiducial states as well as a conditional autocorrelation function g2 = 0.24(6), indicating the single-photon nature of the retrieved photons. In this thesis, a general discussion of the techniques employed and their background theory will be given, followed by a more detailed explanation of this most recent experiment.
by Benjamin Jacob Bloom.
S.B.
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20

Nunnenkamp, Andreas. "Strong correlations in ultracold atomic gases." Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:6e09e9d3-f5cd-4580-a667-6599203162e2.

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In this thesis we investigate strongly-correlated states of ultracold bosonic atoms in rotating ring lattices and arrays of double-well potentials. In the first part of the thesis, we study the tunneling dynamics of ultracold bosons in double-well potentials. In the non-interacting limit single-particle transitions dominate, while in the interaction-dominated regime correlated tunneling of all particles prevails. At intermediate times of the many-particle flopping process correlated states occur, but the timescales of these processes increase dramatically with the number of particles. Using an array of double-well potentials, a large number of such few-particle superposition states can be produced in parallel. In the second part of the thesis, we study the effects of rotation on ultracold bosons confined to one-dimensional ring lattices. We find that at commensurate filling there exists a critical rotation frequency, at which the ground state of the weakly-interacting gas is fragmented into a macroscopic superposition of different quasi-momentum states. We demonstrate that the generation of such superposition states using slightly non-uniform ring lattices has several practical advantages. Moreover, we show that different quasi-momentum states can be distinguished in time-of-flight absorption imaging and propose to probe correlations via the many-body oscillations induced by a sudden change in the rotation frequency. Finally, we compare these macroscopic superposition states to those occurring in superconducting quantum interference devices. In the third part of the thesis, we demonstrate the creation of entangled states with ultracold bosonic atoms by dynamical manipulation of the shape of the lattice potential. To this end, we consider an optical superlattice that allows both the splitting of each site into a double-well potential and the variation of the height of the potential barrier between the sites. We show how to use this array of double-well potentials to perform entangling operations between neighboring qubits encoded on the Zeeman levels of the atoms. As one possible application, we present a method of realizing a resource state for measurement-based quantum computation via Bell-pair measurements. In the final part of the thesis, we study ultracold bosons on a two-dimensional square lattice in the presence of an effective magnetic field and point out a couple of features this system has in common with ultracold bosons in one-dimensional rotating ring lattices.
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21

Jang, Hyounguk. "Interaction of a finite train of short optical pulses with a ladder system." Diss., Kansas State University, 2010. http://hdl.handle.net/2097/7060.

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Doctor of Philosophy
Department of Physics
Brett D. DePaola
In recent years, advance in ultra fast lasers and related optical technology has enhanced the ability to control the interaction between light and matter. In this dissertation, we try to improve our understanding of the interaction of atomic and molecular ladder systems with short optical pulses. A train of pulses produced by shaping the spectral phase of a single pulse from an ultra fast laser allows us to control the step-wise excitation in rubidium (Rb) atoms. As a diagnostic method, we use magneto-optical trap recoil ion momentum spectroscopy (MOTRIMS) to prepare cold target atoms and to observe atomic ions as a result of the interaction. We have explored the interactions of a finite number of optical short pulses in a train with a three-level Rb atom ladder system. Each pulse in the train is separated by a constant time interval with a fixed pulse-to-pulse phase change. In these experiments, two dimensional (2D) landscape maps show the interaction by measuring population in the uppermost state of the ladder system as a function of pulse-to-pulse time interval and phase shift. The observed structures in the 2D landscape are due to constructive or destructive interference in the interaction. Furthermore, different numbers of pulses in the train are applied to the atomic Rb three level ladder system in order to measure the effect on the interaction. The sharpness of the interference structure is enhanced by increasing the number of pulses. This phenomenon is analogous to increasing the sharpness in an optical multi-slit experiment by increasing the number of slits.
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22

Gagnon, Morris Alexis. "Nanolithography using an atomic microscope." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80270.

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In this thesis, I study the nanolithography of gallium arsenide samples by local oxidation with an atomic force microscope (AFM). I examine the current theoretical descriptions of the reaction kinetics and compare the results to experimental data. The main goal is to characterize the AFM oxidation process such that high quality features can be routinely patterned. I also investigate the use of alternative oxidation environments in an attempt to improve the height and aspect ratio of the AFM local oxidation features. An alternative lithography technique involving scratching under a high contact force is also studied. Finally, I discuss the steps that are necessary in order to fabricate a quantum structure with the AFM local oxidation lithography technique.
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23

Holdsworth, P. C. W. "Correlation effects in atomic diffusion." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355755.

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24

Preiss, Philipp Moritz. "Atomic Bose-Hubbard Systems With Single-Particle Control." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:26718727.

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Experiments with ultracold atoms in optical lattices provide outstanding opportunities to realize exotic quantum states due to a high degree of tunability and control. In this thesis, I present experiments that extend this control from global parameters to the level of individual particles. Using a quantum gas microscope for 87Rb, we have developed a single-site addressing scheme based on digital amplitude holograms. The system self-corrects for aberrations in the imaging setup and creates arbitrary beam profiles. We are thus able to shape optical potentials on the scale of single lattice sites and control the dynamics of individual atoms. We study the role of quantum statistics and interactions in the Bose-Hubbard model on the fundamental level of two particles. Bosonic quantum statistics are apparent in the Hong-Ou-Mandel interference of massive particles, which we observe in tailored double-well potentials. These underlying statistics, in combination with tunable repulsive interactions, dominate the dynamics in single- and two-particle quantum walks. We observe highly coherent position-space Bloch oscillations, bosonic bunching in Hanbury Brown-Twiss interference and the fermionization of strongly interacting bosons. Many-body states of indistinguishable quantum particles are characterized by large-scale spatial entanglement, which is difficult to detect in itinerant systems. Here, we extend the concept of Hong-Ou-Mandel interference from individual particles to many-body states to directly quantify entanglement entropy. We perform collective measurements on two copies of a quantum state and detect entanglement entropy through many-body interference. We measure the second order Rényi entropy in small Bose-Hubbard systems and detect the buildup of spatial entanglement across the superfluid-insulator transition. Our experiments open new opportunities for the single-particle-resolved preparation and characterization of many-body quantum states.
Physics
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25

Moore, Michael Glen. "Nonlinear wave mixing between atomic and optical fields." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/289068.

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The interaction between Bose Einstein condensates (BECs) and coherent light fields is treated within the framework of nonlinear wave mixing and studied using techniques developed in the fields of nonlinear and quantum optics. We focus in particular on two situations involving a BEC driven by a strong off-resonant 'pump' laser. First, we consider the case where the laser light is scattered into a single mode of an optical ring cavity. We then consider the case where the light is scattered into the continuum of vacuum modes of the electric field. The first problem is an extension of recent theoretical and experimental work on the so-called collective atomic recoil laser (CARL), whereas the second corresponds to a recent condensate-superradiance experiment performed at MIT. In the cavity situation, we develop a CARL model in which both the atomic and optical fields are treated fully quantum mechanically. We first show that the previous CARL model, which treats the atomic motion classically, breaks down at the recoil temperature due to the effects of matter-wave diffraction. We then show that when combined with a BEC the CARL can be viewed as a device which parametrically amplifies atomic and optical fields. The existence of entanglement and non-classical intensity correlations between the amplified atomic and optical fields is demonstrated, as well as the ability to manipulate the quantum statistical properties of the matter and light waves by injecting a weak laser field into the optical cavity to trigger the device. By replacing the cavity mode with a continuum of modes, we are able to formulate a quantum theory of condensate superradiance in which the scattered light field is eliminated in the Markov approximation. This model shows that condensate depletion leads to mode competition which prevents light scattering in all but the preferred direction(s). The outcome of the mode-competition is highly sensitive to the quantum fluctuations which trigger the phenomenon, resulting in large run-to-run variations in the angular pattern of the superradiant light pulse, an effect which is observed experimentally.
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26

Allehabi, Saleh. "Computational Spectroscopy of C-Like Mg VII." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2018. http://digitalcommons.auctr.edu/cauetds/153.

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In this thesis, energy levels, lifetimes, oscillator strengths and transition probabilities of Mg VII have been calculated. The Hartree-Fock (HF) and Multiconfiguration Hartree-Fock (MCHF) methods were used in the calculations of these atomic properties. We have included relativistic operators mass correction, spin-orbit interaction, one body Darwin term and spin-other-orbit interaction in the Breit-Pauli Hamiltonian. The configurations, (1s2)2s22p2, 2s2p3,2p4, 2s22p3s, 2s22p3p,2s2p2(4P)3s and 2s22p3d which correspond to 52 fine-structure levels, were included in the atomic model for the Mg VII ions. The present results have been compared with NIST compilation and other theoretical results, and generally a good agreement was found.
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27

Busby, David W. "A graphical R-matrix atomic collision environment." Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361356.

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28

McHugh, D. R. "Collisional and radiative studies in atomic spectra." Thesis, University of Newcastle Upon Tyne, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376224.

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29

Shannon, I. "Collisional and radiative effects in atomic spectra." Thesis, University of Newcastle Upon Tyne, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371770.

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30

Ajayi, Olubode Olumuyiwa. "Probe atomisation in electrothermal atomic absorption spectrometry." Thesis, University of Strathclyde, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314558.

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31

Henkel, Carsten, Jean-Yves Courtois, and Alain Aspect. "Atomic diffraction by a thin phase grating." Universität Potsdam, 1994. http://opus.kobv.de/ubp/volltexte/2010/4226/.

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We present a semiclassical perturbation method for the description of atomic diffraction by a weakly modulated potential. It proceeds in a way similar to the treatment of light diffraction by a thin phase grating, and consists in calculating the atomic wavefunction by means of action integrals along the classical trajectories of the atoms in the absence of the modulated part of the potential. The capabilities and the validity condition of the method are illustrated on the well-known case of atomic diffraction by a Gaussian standing wave. We prove that in this situation the perturbation method is equivalent to the Raman-Nath approximation, and we point out that the usually-considered Raman-Nath validity condition can lead to inaccuracies in the evaluation of the phases of the diffraction amplitudes. The method is also applied to the case of an evanescent wave reflection grating, and an analytical expression for the diffraction pattern at any incidence angle is obtained for the first time. Finally, the application of the method to other situations is briefly discussed.
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32

Peyronel, Thibault (Thibault Michel Max). "Quantum nonlinear optics using cold atomic ensembles." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84393.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 219-232).
The fundamental properties of light derive from its constituent particles, photons, which are massless and do no interact with each other. The realization of interactions between photons could enable a wide variety of scientific and engineering applications. In particular, coherent interactions would open the path for the simulation of quantum systems with light. Photon-photon interactions can be mediated by matter, in our case cold atomic ensembles, which provide a nonlinear medium. In conventional nonlinear media, the nonlinearities are negligibly weak at intensities corresponding to single photons and nonlinear optics at the few-photon level is a long-standing goal of optical and quantum science. In this thesis, we report on two different experimental approaches to create optical media with giant nonlinearities. Both approaches rely on Electromagnetically Induced Transparency, in which photons traveling in the medium are best described as part-matter part-light quantum particles, called polaritons. In our first approach, we achieve low-light nonlinearities by loading ensembles of cold atoms in a hollow-core photonic crystal fiber to enhance the polariton-photon interactions. In our second approach, the photons are coupled to strongly interacting Rydberg atoms, which mediate large interactions between single quanta of light. Moreover, the intrinsic nature of these interactions can be tailored to take on a coherent dispersive form.
by Thibault Peyronel.
Ph.D.
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33

Cesar, Claudio Lenz. "Two-photon spectroscopy of trapped atomic hydrogen." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11193.

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34

DiFilippo, Frank. "Precise atomic masses for determining fundamental constants." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/26860.

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35

Miller, Daniel E. (Daniel Edward). "Studying coherence in ultra-cold atomic gases." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/45398.

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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Physics, September 2007.
Includes bibliographical references (leaves 130-141).
This thesis will discuss the study of coherence properties of ultra-cold atomic gases. The atomic systems investigated include a thermal cloud of atoms, a Bose-Einstein condensate and a fermion pair condensate. In each case, a different type of measurement is performed. However, all of the experiments share a common tool: an optical lattice which is used to probe these atomic gases. In the first case, we use an auto-correlation technique to study the interference pattern produced by a gas of atoms, slightly above the Bose -Einstein condensate transition temperature. A moving optical lattice is used to split and recombine the single particle atomic wavefunction. Analogous to a Young's double slit experiment, we observe high contrast interference which is well described by the model which we develop. When we address only a velocity subset of the thermal sample, however, the contrast is enhanced and deviates from this model. In a second experiment we measure the coherence of a diatomic molecular gas, as well as the atomic Bose-Einstein condensate from which it was created. We use Bragg spectroscopy, in which atoms exchange photons with a moving optical lattice, transferring momentum to the atoms. This process can reveal the velocity distribution of the sample as energy and momentum are conserved only for a specific velocity class. Based on this measurement, we find that the atomic coherence is transferred directly to the molecular gas. We also discuss similar preliminary measurements performed on a fermion pair condensate in the BEC-BCS crossover. In a third experiment we study a fermion pair condensate into a 3D optical lattice. Such a system shares many similarities with electrons in solid materials which exhibit superconductivity, and can offer insight into mechanism which result in this behavior. We infer coherence from the sharp interference pattern observed in the expanding gas, after release. Finally, we study the abrupt onset of dissipation observed in a fermion pair condensate, as a function of velocity, in a moving optical lattice.
(cont.) We equate this threshold with the Landau critical velocity, and take measurements throughout the BEC-BCS crossover. The critical velocity is found to be maximum near unitarity, where the loss mechanism is predicted to crossover from phonon-like excitations to pair breaking.
by Daniel E. Miller.
Sc.D.
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36

Roberts, Tony David 1972. "Measuring atomic properties with an atom interferometer." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/29302.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2002.
Includes bibliographical references (p. 177-186).
Two experiments are presented which measure atomic properties using an atom interferometer. The interferometer splits the sodium de Broglie wave into two paths, one of which travels through an interaction region. The paths are recombined, and the interference pattern exhibits a phase shift depending on the strength of the interaction. In the first experiment, the interaction involves a gas. De Broglie waves traveling through the gas experience a phase shift represented by an index of refraction. By measuring the index of refraction at various wavelengths, the predicted phenomenon of glory oscillations in the phase shift has been observed for the first time. The index of refraction has been measured for sodium atoms in gases of argon, krypton, xenon, and nitrogen over a wide range of wavelength. These measurements offer detailed insight into the interatomic potential between sodium atoms and the gases. Theoretical predictions of the interatomic potentials are challenged by these results, which should encourage a renewed effort to better understand these potentials. The second experiment measures atomic polarizability with an atom interferometer. Here, the interaction is with an electric field; the atom experiences a phase shift proportional to its energy inside the field. Previously, this method was used to perform the most accurate (< 1%) measurement of sodium polarizability. The precision was limited, however, by the spread of velocities in the atomic beam-the phase shift is different depending on velocity, and the -interference pattern is washed out.
(cont.) This thesis presents a new technique to "rephase" the interference pattern at large applied fields, and demonstrates a measurement that is free of this limitation. In addition, most of the systematic errors that plagued the previous polarizability measurement are eliminated by the new technique, and an order of magnitude improvement in precision now appears quite feasible. The remaining systematic errors can be eliminated by measuring the ratio of polarizabilities between two different atoms, a comparison whose precision is better by another order of magnitude.
by Tony David Roberts.
Ph.D.
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37

Lucas, David. "A search for parity violation in atomic samarium." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360371.

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38

Blundell, S. "The theory of nuclear effects in atomic spectra." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355731.

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39

James, Jessica. "Nuclear structure effects in atomic parity non-conservation." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259953.

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40

Denton, Bryan John. "The application of diode lasers to atomic spectroscopy." Thesis, University of Newcastle Upon Tyne, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316100.

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41

Braga, J. P. "Adiabatic and non-adiabatic atomic and molecular collisions." Thesis, University of Sussex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375146.

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42

Zingu, Edmund Charles. "Atomic mobility in thin solid Pa2Si films." Doctoral thesis, University of Cape Town, 1985. http://hdl.handle.net/11427/17052.

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Bibliography: pages 210-215.
A theory for the growth kinetics of planar silicide formation in single- and bi-layer metal silicon systems has been developed on the basis that the chemical potential gradient in the growing layer is the driving force for diffusion. The predictions of the theory, when applied to single layer metal-silicon systems, is in agreement with other theories and with experimental results. Planar growth of the outer silicide layer in bilayer metal-silicon systems is predicted to proceed linearly with time, both when controlled by an interfacial reaction and when limited by diffusion through the interposed silicide layer (when this layer is sufficiently thick). In the latter case it is predicted that the growth rate of the outer silicide layer is inversely proportional to the thickness of the interposed layer.
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43

Guo, Yufei. "The local-density-functional theory : application to atoms and molecules." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74535.

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The generalized local-spin-density functional (G-LSD) theory is proposed which avoids (a) the physical restriction used in the generalized exchange local-spin-density functional (GX-LSD) theory; (b) the homogeneous electron-density approximation in the Hartree-Fock-Slater (HFS) theory and in the Gaspar-Kohn-Sham (GKS) theory; and (c) the time-consuming step to search the optimal exchange parameter for each atom or ion in the X$ alpha$ and $ Xi$a theories. Theoretically, the G-LSD theory is more rigorous than the GX-LSD, HFS, GKS, and $ Xi$a theories. Numerically, the statistical total energies for atoms are better in the G-LSD theory than in the GKS theory.
Ionization potentials and electron affinities of atoms, the stability of singly and doubly charged negative ions, and the electronegativities, and hardnesses of the fractional charged atoms with Z $<$ 37 are calculated by the SIC-GX-LSD theory with the GWB Fermi-hole parameters and electron-correlation correction.
The self-interaction correction (SIC) is introduced into the multiple-Scattering X$ alpha$ (MS-X$ alpha$) method and used to calculate some molecules and molecular anions. The results show that the ionization potentials from the negative of the one-electron eigenvalues are as good as those obtained in the transition state calculation and in very good agreement with experiment.
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44

Leroux, Ian Daniel. "Squeezing collective atomic spins with an optical resonator." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68696.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2011.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 128-133).
This thesis describes two methods of overcoming the standard quantum limit of signal-to-noise ratio in atomic precision measurements. In both methods, the interaction between an ultracold atomic ensemble and an optical resonator serves to entangle the atoms and deform the uncertainty distribution of the collective hyperfine spin so that it is narrower in some coordinate than would be possible if the atoms were uncorrelated. The first method uses the dispersive shift of the optical resonator's frequency by the atomic index of refraction to perform a quantum non-demolition measurement of the collective spin, projecting it into a squeezed state conditioned on the measurement outcome. The second method exploits the collective coupling of the atoms to the light field in the resonator to generate an effective interaction that entangles the atoms deterministically. Both methods are demonstrated experimentally, achieving metrologically relevant squeezing of 1.5(5) dB and 4.6(6) dB respectively, and simple analytical models, including the effects of scattering into free space, show that much greater squeezing is realistically achievable. To demonstrate the potential usefulness of such squeezing, a proof-of-principle atomic clock whose Allan variance decreases 2.8(3) three times faster than the standard quantum limit is also presented, together with a discussion of the conditions under which squeezing improves its performance.
by Ian Daniel Leroux.
Ph.D.
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45

Paine, Scott N. "High precision millimeter-wave spectroscopy of atomic hydrogen." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/12864.

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46

Schirotzek, Andre. "Radio-frequency spectroscopy of ultracold atomic Fermi gases." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/77482.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 143-154).
This thesis presents experiments investigating the phase diagram of ultracold atomic Fermi gases using radio-frequency spectroscopy. The tunability of many experimental parameters including the temperature, the interparticle interaction strength and the relative population of different Fermions allows to access very different physical regimes. Radio-frequency spectroscopy has been developed into an ideal tool to probe correlations between particles in these different phases. In particular, radio-frequency spectroscopy of highly population imbalanced atomic Fermi systems gives access to the impurity problem: A single Fermion, or Boson, immersed in a sea of Fermions constitutes a polaron, which can be described by Landau's Fermi liquid theory. A critical interaction strength can be identified separating the regime of a fermionic polaron and a bosonic polaron. Radio-frequency spectroscopy of the polarized superfluid phase allows an accurate measure of the superfluid gap [Delta] and allows to identify the importance of Hartree Mean-field energies. Furthermore, it is shown how these different physical regimes are connected.
by Andre Schirotzek.
Ph.D.
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47

Sandberg, Jon Carl. "Research toward laser spectroscopy of trapped atomic hydrogen." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12659.

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48

Avila, Carlos A. "Laser cooling of a metastable argon atomic beam." FIU Digital Commons, 1996. http://digitalcommons.fiu.edu/etd/1342.

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A production of low velocity and monoenergetic atomic beams would increase the resolution in spectroscopic studies and many other experiments in atomic physics. Laser Cooling uses the radiation pressure to decelerate and cool atoms. The effusing from a glow discharge metastable argon atomic beam is affected by a counterpropagating laser light tuned to the cycling transition in argon. The Zeeman shift caused by a spatially varying magnetic field compensates for the changing Doppler shift that takes the atoms out of resonance as they decelerated. Deceleration and velocity bunching of atoms to a final velocity that depends on the detuning of the laser relative to a frequency of the transition have been observed. Time-of-Flight (TOF) spectroscopy is used to examine the velocity distribution of the cooled atomic beam. These TOF studies of the laser cooled atomic beam demonstrate the utility of laser deceleration for atomic-beam "velocity selection".
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49

Gyawali, Gaurav. "Solving Atomic Wave Functions Using Artificial Neural Networks." ScholarWorks@UNO, 2018. https://scholarworks.uno.edu/honors_theses/104.

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Carleo and Troyer [3] have recently pointed out the possibility of solving quantum many-body problems by using Artificial Neural Networks (ANN). Their work is based on minimizing a variational wave function to obtain the ground states for various spin-dependent systems. This work is primarily focused on developing efficient method using ANN to solve the ground state wave function for atomic systems. We have developed a theoretical groundwork to represent the wave function of a many-electron atom by using artificial neural network while still preserving its antisymmetric property. By using the Metropolis algorithm, Variational Monte Carlo (VMC), and Stochastic Reconfiguration (SR) methods for minimization, we were able to obtain a highly accurate ground state wave function for the He atom. To verify our optimization algorithm, we reproduced the results for the ground state of a three dimensional Simple Harmonic Oscillator (SHO) given by Teng [18].
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50

Drayna, Garrett Korda. "Novel Applications of Buffer-Gas Cooling to Cold Atoms, Diatomic Molecules, and Large Molecules." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:26718757.

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Cold gases of atoms and molecules provide a system for the exploration of a diverse set of physical phenomena. For example, cold gasses of magnetically and electrically polar atoms and molecules are ideal systems for quantum simulation and quantum computation experiments, and cold gasses of large polar molecules allow for novel spectroscopic techniques. Buffer-gas cooling is a robust and widely applicable method for cooling atoms and molecules to temperatures of approximately 1 Kelvin. In this thesis, I present novel applications of buffer-gas cooling to obtaining gases of trapped, ultracold atoms and diatomic molecules, as well as the study of the cooling of large organic molecules. In the first experiment of this thesis, a buffer-gas beam source of atoms is used to directly load a magneto-optical trap. Due to the versatility of the buffer-gas beam source, we obtain trapped, sub-milliKelvin gases of four different lanthanide species using the same experimental apparatus. In the second experiment of this thesis, a buffer-gas beam is used as the initial stage of an experiment to directly laser cool and magneto-optically trap the diatomic molecule CaF. In the third experiment of this thesis, buffer-gas cooling is used to study the cooling of the conformational state of large organic molecules. We directly observe conformational relaxation of gas-phase 1,2-propanediol due to cold collisions with helium gas. Lastly, I present preliminary results on a variety of novel applications of buffer-gas cooling, such as mixture analysis, separation of chiral mixtures, the measurement of parity-violation in chiral molecules, and the cooling and spectroscopy of highly unstable reaction intermediates.
Chemical Physics
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