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1
Hofmann, Julian. "Heralded atom-atom entanglement". Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-164847.
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Treutlein, Philipp. "Coherent manipulation of ultracold atoms on atom chips". Diss., kostenfrei, 2008. http://edoc.ub.uni-muenchen.de/9153/.
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Sun, Bo. "Theoretical studies of atom-atom, atom-photon and photon-photon entanglement". Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-10272006-091504/.
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Thesis (Ph. D.)--Physics, Georgia Institute of Technology, 2007.You Li, Committee Chair ; Citrin David, Committee Member ; Kuzmich Alex, Committee Member ; Fox Ronald, Committee Member ; Chapman Michael, Committee Member.
4
Haffad, Abdelkrim. "Angular momentum transfer in electron-atom and atom-atom collisional ionization". Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/29826.
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Pax, Paul Henry 1958. "Few-atom effects in atom optics". Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/288794.
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Despite the many advances and achievements in the fields of atom optics and atom cooling, there remains a wealth of dynamical detail to be filled in. While the main features of the important phenomena of atomic cooling, trapping and manipulation by electromagnetic fields are well understood, there are interesting subsidiary effects that are worth our attention. An example, which we discuss in Ch. 5 is the discovery that atomic diffusion in optical lattices may not follow the normal diffusion equation. The work reported in this dissertation represents an investigation into possible few-body effects in some atom optical configurations of interest. The effects of indistinguishability, through the exchange force, on atomic diffraction by standing wave light fields is considered in Ch. 2. In Ch. 3, after a brief overview of atomic collisions in light fields, we look at the role that the dipole-dipole interaction might play, again in atomic diffraction. Chapters 4 and 5 are concerned with optical lattices, and lay the ground work for a study of the effect of the dipole-dipole interaction on the dynamics of atoms confined in such lattices.
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Menzel, Thomas. "Elektronentranslation in Atom-Atom-Stössen bei niedriger Energie". [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=959598227.
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Spratt, David James. "Electron loss and excitation in atom-atom collisions". Thesis, Queen's University Belfast, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287429.
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Featonby, Paul. "Atom interferometry". Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390459.
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Hofmann, Julian [Verfasser], i Harald [Akademischer Betreuer] Weinfurter. "Heralded atom-atom entanglement / Julian Hofmann. Betreuer: Harald Weinfurter". München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1047062313/34.
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Baker, Mark. "Metastable Atom Lithography". Thesis, Griffith University, 2008. http://hdl.handle.net/10072/365477.
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This thesis describes the development of a rare gas metastable atomic beam apparatus, and its application to atom lithography. The principal component of the apparatus is the supersonic DC discharge source. The source parameters, such as operating pressure, skimmer distance, discharge current and nozzle shape were optimised to generate a bright beam of excited state metastable neon and argon, with typical flux of 5×10¹? atoms sr?¹ and 3×10¹? atoms sr?¹ respectively. This apparatus was used to investigate the pattern formation of self assembled monolayer (SAM) resists prepared on Au/Si samples exposed to metastable beams of Ar* and Ne*, through microfabricated contact masks. Positive and negative tone patterning was observed, with supporting XPS analysis attributing the negative tone resists to contamination from pump oil vapour. The formation of negative tone contamination resists by the metastable neon beam was applied to the generation of micrometer sized Fe structures using contact masks. A 3-step etch process was developed and refined, resulting in 7.5µm Fe microdot structures on a Si substrate. A bright transverse and longitudinally cooled and collimated metastable neon beam source for atom lithography was developed. The transverse atomic beam collimation stage produced a collimated beam flux of of 1.4×10¹? s?¹, with a divergence of 22.8 mrad. Axial slowing of the atomic beam was demonstrated with the development of a Zeeman slower. Numerical simulations were undertaken to calculate the motion of metastable neon atoms in a one-dimensional standing wave light field mask. The simulations show the dynamics and atom distributions for the focusing regime (low power) and channeling regime (high power). Future refinements of the apparatus should allow the realisation of nanofabricated structures utilising optical masking techniques.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Physical Sciences
Faculty of Science
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Roux, Matthew John. "ATOM : a distributed system for video retrieval via ATM networks". Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/21327.
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The convergence of high speed networks, powerful personal computer processors and improved storage technology has led to the development of video-on-demand services to the desktop that provide interactive controls and deliver Client-selected video information on a Client-specified schedule. This dissertation presents the design of a video-on-demand system for Asynchronous Transfer Mode (ATM) networks, incorporating an optimised topology for the nodes in the system and an architecture for Quality of Service (QoS). The system is called ATOM which stands for Asynchronous Transfer Mode Objects. Real-time video playback over a network consumes large bandwidth and requires strict bounds on delay and error in order to satisfy the visual and auditory needs of the user. Streamed video is a fundamentally different type of traffic to conventional IP (Internet Protocol) data since files are viewed in real-time, not downloaded and then viewed. This streaming data must arrive at the Client decoder when needed or it loses its interactive value. Characteristics of multimedia data are investigated including the use of compression to reduce the excessive bit rates and storage requirements of digital video. The suitability of MPEG-1 for video-on-demand is presented. Having considered the bandwidth, delay and error requirements of real-time video, the next step in designing the system is to evaluate current models of video-on-demand. The distributed nature of four such models is considered, focusing on how Clients discover Servers and locate videos. This evaluation eliminates a centralized approach in which Servers have no logical or physical connection to any other Servers in the network and also introduces the concept of a selection strategy to find alternative Servers when Servers are fully loaded. During this investigation, it becomes clear that another entity (called a Broker) could provide a central repository for Server information. Clients have logical access to all videos on every Server simply by connecting to a Broker. The ATOM Model for distributed video-on-demand is then presented by way of a diagram of the topology showing the interconnection of Servers, Brokers and Clients; a description of each node in the system; a list of the connectivity rules; a description of the protocol; a description of the Server selection strategy and the protocol if a Broker fails. A sample network is provided with an example of video selection and design issues are raised and solved including how nodes discover each other, a justification for using a mesh topology for the Broker connections, how Connection Admission Control (CAC) is achieved, how customer billing is achieved and how information security is maintained. A calculation of the number of Servers and Brokers required to service a particular number of Clients is presented. The advantages of ATOM are described. The underlying distributed connectivity is abstracted away from the Client. Redundant Server/Broker connections are eliminated and the total number of connections in the system are minimized by the rule stating that Clients and Servers may only connect to one Broker at a time. This reduces the total number of Switched Virtual Circuits (SVCs) which are a performance hindrance in ATM. ATOM can be easily scaled by adding more Servers which increases the total system capacity in terms of storage and bandwidth. In order to transport video satisfactorily, a guaranteed end-to-end Quality of Service architecture must be in place. The design methodology for such an architecture is investigated starting with a review of current QoS architectures in the literature which highlights important definitions including a flow, a service contract and flow management. A flow is a single media source which traverses resource modules between Server and Client. The concept of a flow is important because it enables the identification of the areas requiring consideration when designing a QoS architecture. It is shown that ATOM adheres to the principles motivating the design of a QoS architecture, namely the Integration, Separation and Transparency principles. The issue of mapping human requirements to network QoS parameters is investigated and the action of a QoS framework is introduced, including several possible causes of QoS degradation. The design of the ATOM Quality of Service Architecture (AQOSA) is then presented. AQOSA consists of 11 modules which interact to provide end-to-end QoS guarantees for each stream. Several important results arise from the design. It is shown that intelligent choice of stored videos in respect of peak bandwidth can improve overall system capacity. The concept of disk striping over a disk array is introduced and a Data Placement Strategy is designed which eliminates disk hot spots (i.e. Overuse of some disks whilst others lie idle.) A novel parameter (the B-P Ratio) is presented which can be used by the Server to predict future bursts from each video stream. The use of Traffic Shaping to decrease the load on the network from each stream is presented. Having investigated four algorithms for rewind and fast-forward in the literature, a rewind and fast-forward algorithm is presented. The method produces a significant decrease in bandwidth, and the resultant stream is very constant, reducing the chance that the stream will add to network congestion. The C++ classes of the Server, Broker and Client are described emphasizing the interaction between classes. The use of ATOM in the Virtual Private Network and the multimedia teaching laboratory is considered. Conclusions and recommendations for future work are presented. It is concluded that digital video applications require high bandwidth, low error, low delay networks; a video-on-demand system to support large Client volumes must be distributed, not centralized; control and operation (transport) must be separated; the number of ATM Switched Virtual Circuits (SVCs) must be minimized; the increased connections caused by the Broker mesh is justified by the distributed information gain; a Quality of Service solution must address end-to-end issues. It is recommended that a web front-end for Brokers be developed; the system be tested in a wide area A TM network; the Broker protocol be tested by forcing failure of a Broker and that a proprietary file format for disk striping be implemented.
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Holst, B. "Atom optics and surface growth studies using helium atom scattering". Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604194.
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The first part of thesis investigates the application of electrostatically deformed single crystal membranes as focusing elements for a neutral atomic beam in an ultra high resolution diffractometer. The second part demonstrates the versatility of helium as a surface science tool in a study of the growth of ultra thin Cu-films on Pt(111). Chapter 1 gives an introduction to the subject of atom focusing with an overview of the various methods hitherto applied. Chapter 2 presents a theoretical framework for the application of a focusing element in an ultra high resolution diffractometer. An off axis reflected ray equation is derived from which aberration coefficients are obtained and used to determine the best obtainable performance. Chapter 3 presents equations for calculating deformation of radically symmetric thin plates (membranes). Furthermore interferometry experiments are presented which investigate the deformation of single crystal Au(100) and Si(100) in varying fields. The films mechanical properties are discussed, and contourmaps obtained from the interferometry experiments used in computer simulations to evaluate their focusing properties. Chapter 4 contains the experimental methods and sample preparation of the two types of samples used here. The Pt(111) and the Si(111)-H(1 x 1) eventually chosen for the mirror. In particular a new mount specially designed for the focusing mirror is described in detail.
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Hüper, Andreas [Verfasser]. "Accurate atom counting for entanglement-enhanced atom interferometry / Andreas Hüper". Hannover : Gottfried Wilhelm Leibniz Universität Hannover, 2020. http://d-nb.info/1211083845/34.
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Ribeiro, Sofia. "Atom-surface interactions with Rydberg atoms : an application to hybrid systems". Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/24166.
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This thesis focuses on theoretical quantum optics, with special emphasis on developing protocols in which engineered vacuum forces enable one to construct hybrid systems. In these systems, atoms are combined with solid-state devices in order to take advantage of their unique properties such as long coherence times of atoms and flexibility, tunability, scalability, and fast response offered by solid-state systems. Special attention is given to the study of atom-surface interactions with Rydberg atoms, where exact Fano-type diagonalization of the interaction Hamiltonian is obtained showing that, not only do Rydberg atoms suffer energy shifts, the presence of a surface leads to an alteration and admixture of the unperturbed eigenstates. Of particular interest are dispersion forces on graphene systems. We investigate whether and under which circumstances the Casimir-Polder potential between an atom and a graphene-substrate system is dominated by the interaction with graphene such that the effect of the substrate does not play an important role. We also explore the possibility to create a setup where dispersion forces could be use to bend a graphene sheet. Placing an atom close, at distances of a few hundred nanometers, to a free-standing graphene membrane we show that temporal changes in the atomic state change the Casimir-Polder interaction, thereby leading to the creation of a backaction force in the graphene sheet. Finally, we look at nonlinear atom--surface coupling processes with the aim of proposing a hybrid quantum circuit device in which individual field-excitations can be transferred between atoms and surface polaritons on demand. Deeper investigations of nonlinear processes reveal the existence of a sum rule for two-photon spontaneous decay rates that can be simply understood as a redistribution of photonic modes across the frequency spectrum where the total integrated number of modes is still conserved.
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Palmer, Adam J. "A UV Free Source of Metastable Neon Atoms for Atom Lithography". Thesis, Griffith University, 2011. http://hdl.handle.net/10072/367006.
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A high flux metastable Neon atomic beam was designed and characterised. Atom
optical enhancement of the beam using a two-dimensional optical collimator, novel
two beam Zeeman slower and hexapole magnetic guide was performed to produce a
UV-free metastable flux of (4.35 × 109 ± 4 × 107) atoms s−1.
Investigations of several resists for neutral atom lithography were undertaken. A
quantitative investigation of the wetting properties of ethanethiol (ET) and dodecanethiol
(DDT) self-assembled monolayers (SAM’s) exposed to various metastable
dosages was carried out. A mechanism for the poor lithographic patterning using
ET was proposed and the negative contrast patterning observed for this SAM was
similar to those observed for bare gold substrates and were attributed to mechanical
pump oil (MPO) contamination resists.
Negative patterned resists were used to produce 7.5 μm iron dots on a silicon
substrate via neutral atom lithography. This scheme was found to be very robust
and free from the laser cooling issues of alternative direct depositional schemes. Numerical
simulations have shown that two dimensional arrays of magnetic nanodots
may be produced this way, paving the way for a magnetic storage option with a
density of " 0.1 Gbit mm−2.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Physical Sciences
Science, Environment, Engineering and Technology
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Volz, Jürgen. "Atom-Photon Entanglement". Diss., lmu, 2006. http://nbn-resolving.de/urn:nbn:de:bvb:19-56356.
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MacDonald, Fred G. R. S. "Positronium - atom scattering". Thesis, Queen's University Belfast, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268233.
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Kash, Michael Mason. "Rydberg atom diamagnetism". Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14367.
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Byrd, Tommy. "Ballistic atom pumps". W&M ScholarWorks, 2015. https://scholarworks.wm.edu/etd/1539623999.
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Researchers have long been interested in electron transport through mesojunctions containing time-dependent potential energies, a process often called "quantum pumping." A useful model of such a system is a ballistic atom pump, which consists of two reservoirs of neutral ultracold atoms connected by a channel containing oscillating repulsive potential-energy barriers. Under certain conditions, such pumps can create net transport of atoms from one reservoir to the other, and energy can be pumped out of or into each reservoir even when there is no net particle transport. These pumps are studied from classical and quantum-mechanical perspectives, and semiclassical theory is used to explain some scattering properties which are not easily explained by quantum theory. This system is also a nice model of chaotic transport. Escape-time plots showing the time for classical trajectories to escape the barrier region display a type of fractal self-similarity. A topological theory using a discrete map of the system in the phase plane is developed, and this theory predicts and explains the features seen in escape-time plots.
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Goldstein, Elena Vladimirovna 1962. "Nonlinear atom optics". Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/289255.
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In contrast to electromagnetic fields, matter-wave fields are intrinsically interacting due to the presence of atom-atom collisions. Hence, matter-wave optics becomes effectively nonlinear as soon as the atomic densities are high enough that collisions can no longer be ignored. The goal of this dissertation is to study selected aspects of atom optics under such conditions. Specifically, Chapter 2 studies the near-resonant dipole-dipole interaction between two atoms in tailored vacua. In contrast to spontaneous emission, whose rate is known to be influenced by the type of vacuum the atom interacts with, we find that the dipole-dipole potential is determined only by the free space vacuum and is not modified either by thermal or squeezed vacua. In addition in the far off-resonance regime we find that the squeezed vacuum results in an additional contribution to the effective potential governing the evolution of the atomic ground state. In the second part of the dissertation, which comprises Chapter 3, we then study several aspects of the many-body theory of atomic ultracold systems in situations where the nonlinearity arises due to the two-body dipole-dipole interaction. After a formal theoretical development we discuss the possibility of using atomic phase conjugation off Bose condensates as a diagnostic tool to access the spatial coherence properties and to measure the lifetime of the condensate. We argue that phase conjugation provides an attractive alternative to the optical methods of probing condensate proposed in the past. We further study the elementary excitations in a multicomponent Bose condensates and determine the quasi-particle frequency spectrum. We show that in that case interferences resulting from cross-coupling between the condensate components can lead to a reversal of the sign of the effective two-body interaction and to the onset of spatial instabilities.
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Perreault, John D. "Using Atom Optics to Measure van der Waals Atom-Surface Interactions". Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1317%5F1%5Fm.pdf&type=application/pdf.
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Gangloff, Dorian Armand. "Nanocontacts controlled atom-by-atom in an ion-crystal friction emulator". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104459.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016.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 (pages 187-200).
Friction is the basic, ubiquitous mechanical interaction between two surfaces that results in resistance to motion and energy dissipation. To test long-standing atomistic models of friction processes at the nanoscale, we implemented a synthetic nanofriction interface between a laser-cooled Coulomb crystal of individually addressable ions as the moving object and a periodic light-field potential as the substrate. Through a variety of experiments presented in this thesis, we show atom-by-atom and with high spatial resolution that friction at the nanoscale can substantially differ from the simple phenomenological laws observed at the macroscale. Namely, we show that atomic-scale stick-slip friction can be tuned from maximal to nearly frictionless via arrangement of the ions relative to the periodic potential, and study the associated transition in transport dynamics as manifested by the propagation of kinks. We show that friction depends on velocity and temperature, in excellent agreement with simple analytical models, and that in the appropriate velocity regime, the dynamics can be observed in a way that is effectively at zero-temperature. We also establish a direct link between Aubry's structural transition for an infinite chain in an incommensurate periodic potential, and the vanishing of friction in nanocontacts. Our model system enables a microscopic and systematic investigation of friction, potentially even into the quantum many-body regime.
by Dorian Armand Gangloff.
Ph. D.
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Miroshnychenko, Yevhen. "An atom sorting machine". [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=98096489X.
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Patton, Forest S. "Coherent atom beam diffraction /". view abstract or download file of text, 2005. http://wwwlib.umi.com/cr/uoregon/fullcit?p3190537.
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Thesis (Ph. D.)--University of Oregon, 2005.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 81-83). Also available for download via the World Wide Web; free to University of Oregon users.
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Trupke, Michael. "Microcavities for atom chips". Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491114.
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This thesis describes the development and implementation of fibre-coupled, micron-scale optical resonators for the detection and manipulation of neutral atoms. The resonators are intended for integration with atom chips. The latter are microfabricated devices which enable the cooling, trapping, gUiding and manipulation of atoms by means of optical, magnetic and electric fields. The fields are generated in part using micro-fabricated features on the surface of the chips. Optical cavities are among the most important tools in the study of the interactions between light and matter. They allow the observation of fundamental processes in quantum optics, based on the enhanced coupling of atomic transitions to light fields. Our resonators have mode volumes which are two orders of magnitude smaller than those used in typical cavity quantum electrodynamics experiments. Together with their high quality factors, this leads to large enhancement factors, rendering them ideal for the detection and manipulation of atoms on chips. They are scalable and directly fibre-coupled, both of which are qualities of interest for their implementation in quantum information-processing applications. In the thesis, the optical characteristics of the resonators are explained, as well as the basic principles of the interaction of atoms with their light field. The setup used for the test implementation of the devices is presented, together with early experimental results. These include the detection of atoms via their effect on the cavity reflection spectrum, and the detection of enhanced atomic fluorescence into the cavity mode. The thesis concludes with an outlook on further experimentation, possible improvements of the devices themselves, and a view on their integration with existing atom chip technology.
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Ding, Shijie. "Atom transfer radical polymerization". Laramie, Wyo. : University of Wyoming, 2006. http://proquest.umi.com/pqdweb?did=1225138911&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Keehan, Michael Stephen. "Termolecular ion-atom association". Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/29445.
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Patel, Akshay. "Intense laser atom interactions". Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341059.
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Scott, Martin. "Atom : squeezed light interactions". Thesis, Queen's University Belfast, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268311.
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Vernier, Aline. "Phase dependent atom optics". Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2560/.
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Quantum interference in atomic media has elicited interest for a very wide range of investigations and applications. As well as being a fascinating effect in itself, it also found applications in spectroscopy, nonlinear optics and has recently been drawing attention in the field of quantum optics for the realisation of sources of entangled photons, optical switching, and quantum information storage. The work presented in this thesis consists of two main projects centred around the theme of quantum interference in atomic processes. As cooled atomic vapours provide favourable conditions for the investigation of coherent phenomena, a magneto-optical trap was built for the future study of quantum interference in four-level link- ages. The number of trapped atoms is estimated to be ≈ 8 × 10^8, and the density to be ≈ 10^9 atoms per cubic centimetre. This represents the first stage of an ongoing study of quantum interference in four-level linkages. However, coherent effects can also be observed in hot vapours. A spontaneous, highly efficient, frequency up-conversion arising from four-wave mixing can indeed be observed in Rubidium. This complex phenomenon was investigated experimentally and theoretically so as to improve the conversion efficiency, and understand the underlying physics. The optimum conditions found in this study yield 1 mW of converted light for 40 mW of pumping light. As part of the study of the phase coherence of the process, the conversion of spatial modes in the four-wave mixing process was also examined. The observation of the transfer of orbital angular momentum in the process is reported, and a preliminary theoretical interpretation is presented.
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Sieker, Anke. "Oxygen atom transfer reactions". Thesis, University of Edinburgh, 1994. http://hdl.handle.net/1842/12933.
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Oxygen atom transfer reactions in a series of early transition metal complexes in both solution and solid state were investigated, with a particular interest in O-atom transfer processes from bonded NOx (x= 1,2,3) ligands to adjacent carbonyl groups. The main objective was the synthesis and characterisation of new mixed CO/NO2- species. In Chapter 1 a general review of oxygen atom transfer reactions involving CO and NOx is given. Chapter 2 presents the results gained from reactions of M2(CO)10, ClM(CO)5 and several other carbonyl halides {M=Mn, Re} with [PPN][NO2]/[PPh4][NO2]. Chemical activation by (CH3)3NO prior to interaction with [PPN][NO2]/PPh4][NO2] has also been investigated. Complexes isolated and characterised by IR spectroscopy and X-ray diffraction include [(OC)3Mn(μ2-NO(O))2(μ2-O(NO))Mn(μ2-NO(O))2(μ2-O(NO))Mn(CO)3](PPN)2, {[CIRe(CO)3(NO2)2]C1[(CH3)3NCH2C1]3} and [Re(CO)3(ONO)3](PPN)2. Compounds such as Mn2(CO)8(PPh3)2, [Mn(CO)4C1(PPh3)] and [trans-Mn(CO)3C1(PPh3)2] substituted in part by tertiary phosphines have been tested towards their reactivity with [PPN][NO2]/[PPh4][NO2]. Reaction pathways are discussed on the basis of detailed IR spectroscopy studies. In Chapter 2.3. reactions of M(CO)6, [M(CO)5C1](Et4) {M= Cr, Mo and W} and [(OC)3Mo(μ2-C1)3Mo(CO)3](NEt4)2 with [PPN][NO2]/[PPh4](NO2] are presented. Mixed CO/NO2 species were prepared for all three metals and structurally characterised in the solid state in form of [M(CO)5(NO2)](PPh4) {M=Cr and W}. Mixed CO/NO complexes of Manganese (2.1.3.) and Chromium (2.3.2.) have been synthesised and their reactions with O2 investigated. Oxidation of the nitrosyl ligands was observed in both cases and possible reaction mechanisms are presented.
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Szmuk, Ramon. "Atom chips for metrology". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066089/document.
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Cette thèse porte sur deux sujets principaux: l'évaluation de la stabilité d'une horloge sur microcircuit utilisant des atomes piégés (Trapped Atom Clock on a Chip - TACC) et l'extension de cette technologie vers la réalisation d'un interféromètre atomique sur la même puce. Cette combinaison constitue la base pour la réalisation de capteurs inertiels intégrés pour la navigation. Des travaux antérieurs ont installé l'horloge et ont découvert, entre autres, des temps de cohérence très longs, qui permettent une interrogation Ramsey jusqu'à 5 s, une condition préalable pour le fonctionnement à grande stabilité. Je présente ici la première évaluation approfondie de la stabilité de l'horloge. Avec mon prédécesseur, nous avons démontré les fluctuations de fréquences relatives de 5.8 10-13 à 1 s intégrant jusqu'à 6 10-15 à 30000 s.La deuxième partie de cette thèse vise à étendre la polyvalence de notre puce atomique pour créer un interféromètre. J'ai étudié divers régimes d'interféromètres en utilisant des potentiels habillés par microondes. Le premier régime consiste à déplacer l'un des états d'horloge verticalement pendant une séquence d'horloge Ramsey. Ceci permet la mesure de gradients de potentiel en exploitant la différence de fréquences entre les deux états. Le second régime utilise des champs microondes pour générer un potentiel de double puits dans l'un des états d'horloge et un seul puits dans l'autre.À partir du seul puits, un pulse-π sur la transition d'horloge constitue la séparatrice de l'interféromètre et conduit une séparation spatiale tout en préservant le même état interne pour les deux bras de l'interféromètreThis thesis covers two main subjects: the evaluation of the stability of a Trapped Atom Clock on a Chip (TACC) and the expansion of this technology towards creating an atom interferometer on the same chip. The combination of a clock and an interferometer on the same chip constitutes the basis for the realization of atom-based integrated inertial navigation units. Previous work installed the clock operation and discovered, among others, very long coherence times, which allow Ramsey interrogations of up to 5 s, a prerequisite for high stability operation. I present the first thorough evaluation of the clock stability. Together with my predecessor we have demonstrated relative frequency fluctuations of 5.8 10-13 at 1 s integrating down to 6 10-15 at 30,000 s. The second part of this thesis aims to expand the versatility of our atom chip to create an atom interferometer. I have studied various interferometer schemes using microwave dressed potentials and implemented these to the set-up. The first scheme, following work by P. Treutlein et al., involves displacing one of the clock states vertically during a Ramsey clock sequence thereby allowing the measurement of potential gradients by exploiting the differential frequency shift accumulated between the two states. Ramsey fringes where recorded for different durations of the splitting, resulting in a clear signal of the wavepacket separation. The second scheme uses microwave dressing to generate a double well potential in one of the clock states and a single well in the other. Starting in the single well, a π-pulse on the clock transition constitutes the beam splitter and leads to a spatial separation for the same internal state
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Hayes, W. W. "Atom scattering from metals". Connect to this title online, 2009. http://etd.lib.clemson.edu/documents/1263396718/.
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Taylor, Byron Brooks 1965. "Topics in atom optics". Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/289433.
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This dissertation covers the field of atom optics and is divided into four main chapters: In Chapter 2 we investigate the effects of light forces on the center-of-mass motion of two-level atoms. This will lead to the discussion of two regimes: the "ray optic" and the "wave optic" regime. In the first case, an atom is well localized in the field which allows a comparison to be made with classical ray optics. In the second case, the atom is strongly delocalized which leads to a wave treatment and allows a comparison with diffractive optics. We finish this chapter with an example in each regime: Doppler cooling for ray optics and an atomic Fabry-Perot for wave optics. In Chapter 3 we extend the results of the previous chapter to the diffraction of atoms by a standing light field. We cover three regimes in the near resonant Kapitza-Dirac effect: the Raman-Nath, the Bragg and the optical Stern-Gerlach regime. In the Raman-Nath and Bragg regimes, the wave-packet is strongly delocalized compared to the period of the standing wave. In contrast, the Stern-Gerlach regime has a small spatial extent. The Raman-Nath and Bragg regimes are differentiated in their treatment of the kinetic energy. Initially we only discuss coherent interactions. In the later half of this chapter we introduce spontaneous emission and show how its presence affects the diffraction pattern in each of these regimes. In Chapter 4 we cover various atomic cooling schemes: strong field Sisyphus cooling, adiabatic cooling, evaporative cooling, polarization gradient cooling and velocity selective coherent population trapping. We begin with a brief discussion of atomic temperature. We then cover two cooling schemes for two-level atoms. We eventually move to multi-level atoms and end this chapter with a two-atom multi-level system. In Chapter 5 we conclude with a brief discussion of practical uses and devices that may arise from atom optics such as lenses, mirrors, gravitational interferometry, lithography and atomic clocks.
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Witham, Philip James. "Pinhole Neutral Atom Microscopy". PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1407.
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This work presents a new form of microscopy, the instrument constructed to demonstrate it, the images produced and the image contrast mechanisms seen for the first time. Some of its future scientific potential is described and finally, recent work towards advancing the method is discussed.
Many forms of microscopy exist, each with unique advantages. Of several broad categories that they could be grouped into, those that use particle beams have proven very generally useful for micro and nano-scale imaging, including Scanning Electron, Transmission Electron, and Ion Beam microscopes. These have the disadvantage, however, of implanting electric charges into the sample, and usually at very high energy relative to the binding energy of molecules. For most materials this modifies the sample at a small scale and as we work increasingly towards the nano-scale, this is a serious problem.
The Neutral Atom Microscope (NAM) uses a beam of thermal energy (under 70 meV) non-charged atoms or molecules to probe an atomic surface. For several decades scientists have been interested in this possibility, using a focused beam. Scattering of neutral atoms provides a uniquely low-energy, surface-sensitive probe, as is known from molecular beam experiments.
We have developed a new approach, operating with the sample at a close working distance from an aperture, the need for optics to focus the beam is obviated. The demonstrated, practical performance of this "Pinhole" NAM exceeds all other attempts by great lengths by many measures. The unique images resulting and contrast mechanism discoveries are described. The future potential for nano-scale resolution is shown.
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Whitlock, Shannon, i n/a. "Bose-Einstein condensates on a magnetic film atom chip". Swinburne University of Technology, 2007. http://adt.lib.swin.edu.au./public/adt-VSWT20070613.172308.
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Atom chips are devices used to magnetically trap and manipulate ultracold atoms
and Bose-Einstein condensates near a surface. In particular, permanent magnetic film
atom chips can allow very tight confinement and intricate magnetic field designs while
circumventing technical current noise. Research described in this thesis is focused
on the development of a magnetic film atom chip, the production of Bose-Einstein
condensates near the film surface, the characterisation of the associated magnetic
potentials using rf spectroscopy of ultracold atoms and the realisation of a precision
sensor based on splitting Bose-Einstein condensates in a double-well potential.
The atom chip itself combines the edge of a perpendicularly magnetised GdTbFeCo
film with a machined silver wire structure. A mirror magneto-optical trap collects
up to 5 x 108 87Rb atoms beneath the chip surface. The current-carrying wires
are then used to transfer the cloud of atoms to the magnetic film microtrap and
radio frequency evaporative cooling is applied to produce Bose-Einstein condensates
consisting of 1 x 105 atoms.
We have identified small spatial magnetic field variations near the film surface that
fragment the ultracold atom cloud. These variations originate from inhomogeneity in
the film magnetisation and are characterised using a novel technique based on spatially
resolved radio frequency spectroscopy of the atoms to map the magnetic field landscape
over a large area. The observations agree with an analytic model for the spatial decay
of random magnetic fields from the film surface.
Bose-Einstein condensates in our unique potential landscape have been used as a
precision sensor for potential gradients. We transfer the atoms to the central region
of the chip which produces a double-well potential. A single BEC is formed far from
the surface and is then dynamically split in two by moving the trap closer to the
surface. After splitting, the population of atoms in each well is extremely sensitive to
the asymmetry of the potential and can be used to sense tiny magnetic field gradients
or changes in gravity on a small spatial scale.
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Hu, Zhen Kimble H. Jeff Kimble H. Jeff. "Quantum optics with cold atoms--nonlinear spectroscopy and road toward single-atom trap /". Diss., Pasadena, Calif. : California Institute of Technology, 1995. http://resolver.caltech.edu/CaltechETD:etd-10112007-092812.
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Izadi, Saeed. "Optimal Point Charge Approximation: from 3-Atom Water Molecule to Million-Atom Chromatin Fiber". Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/81539.
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Atomistic modeling and simulation methods enable a modern molecular approach to bio-medical research. Issues addressed range from structure-function relationships to structure-based drug design. The ability of these methods to address biologically relevant problems is largely determined by their accurate treatment of electrostatic interactions in the target biomolecular structure. In practical molecular simulations, the electrostatic charge density of molecules is approximated by an arrangement of fractional "point charges" throughout the molecule. While chemically intuitive and straightforward in technical implementation, models based exclusively on atom-centered charge placement, a major workhorse of the biomolecular simulations, do not necessarily provide a sufficiently detailed description of the molecular electrostatic potentials for small systems, and can become prohibitively expensive for large systems with thousands to millions of atoms. In this work, we propose a rigorous and generally applicable approach, Optimal Point Charge Approximation (OPCA), for approximating electrostatic charge distributions of biomolecules with a small number of point charges to best represent the underlying electrostatic potential, regardless of the distance to the charge distribution. OPCA places a given number of point charges so that the lowest order multipole moments of the reference charge distribution are optimally reproduced. We provide a general framework for calculating OPCAs to any order, and introduce closed-form analytical expressions for the 1-charge, 2-charge and 3-charge OPCA. We demonstrate the advantage of OPCA by applying it to a wide range of biomolecules of varied sizes. We use the concept of OPCA to develop a different, novel approach of constructing accurate and simple point charge water models. The proposed approach permits a virtually exhaustive search for optimal model parameters in the sub-space most relevant to electrostatic properties of the water molecule in liquid phase. A novel rigid 4-point Optimal Point Charge (OPC) water model constructed based on the new approach is substantially more accurate than commonly used models in terms of bulk water properties, and delivers critical accuracy improvement in practical atomistic simulations, such as RNA simulations, protein folding, protein-ligand binding and small molecule hydration. We also apply our new approach to construct a 3-point version of the Optimal Point Charge water model, referred to as OPC3. OPCA can be employed to represent large charge distributions with only a few point charges. We use this capability of OPCA to develop a multi-scale, yet fully atomistic, generalized Born approach (GB-HCPO) that can deliver up to 2 orders of magnitude speedup compared to the reference MD simulation. As a practical demonstration, we exploit the new multi-scale approach to gain insight into the structure of million-atom 30-nm chromatin fiber. Our results suggest important structural details consistent with experiment: the linker DNA fills the core region and the H3 histone tails interact with the linker DNA. OPC, OPC3 and GB-HCPO are implemented in AMBER molecular dynamics software package.Ph. D.
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Gehr, Roger Peter. "Cavity based high-fidelity and non-destructive single atom detection on an atom chip". Paris 6, 2011. http://www.theses.fr/2011PA066087.
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Dans ce mémoire, nous démontrons la préparation et la détection d’atomes uniques sur une puce à atomes. Nous préparons un atome unique de Rubidium couplé fortement à un résonateur optique de haute finesse intégrée à la puce à atomes. L’atome est extrait d’un condensat de Bose-Einstein et piégé à une position de couplage maximum au résonateur. Nous mesurons le spectre du système couplé et démontrons qu’il se situe dans le régime de couplage fort d’électrodynamique quantique. Ceci nous permet d’utiliser la transmission et la réflexion du résonateur pour déduire l’état hyperfine de l’atome piégé. Nous obtenons une fidélité de détection de 99. 93% avec un temps de détection de 100 microsecondes. L’atome reste piégé pendant la détection. Cette performance est comparable aux expériences d’ions piégés et est compatible avec des techniques de correction d’erreurs dans le cadre de l’information quantique. Nous mesurons également le taux de diffusion de photons pendant la détection, et démontrons que nous détectons l’état interne de l’atome avec une erreur inférieure à 10% en diffusant moins de 0. 2 photons en moyenne. Pour conclure la caractérisation du processus de détection, nous analysons la projection de l’état atomique due à la mesure en effectuant une expérience de type Zeno quantique. Nous démontrons que chaque photon incident sur la cavité réduit la cohérence de l’état atomique d’un facteur de 0. 7. La détection présentée est donc proche de l’exemple type d’une mesure projective d’un system quantique à deux niveaux
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Ferreira, Cláudia Pio. "Alinhamento Iônico na fotoionização do átomo de hélio por luz polarizada". Universidade de São Paulo, 1997. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-19092008-095832/.
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Neste trabalho, descrevemos os conceitos de alinhamento e orientação baseados no formalismo de Fano e Macek e estudamos a fotoionização do estado fundamental do átomo de Hélio. Para isso usou-se uma função de onda aproximada obtida a partir da diagonalização do operador de Gailitis- Damburg. A anisotropia do sistema formado após a colisão foi caracterizada através do cálculo da densidade eletrônica do íon e através do tensor de alinhamento e do vetor de orientação. O comportamento destes parâmetros para as transições n? -> 1s e n->n-1 em função de n (número quântico principal do íon) foi graficado para as duas simetrias relevantes, 1P° e 3P°. Observamos que o alinhamento máximo do sistema, em relação ao eixo de maior simetria definido como sendo o eixo z ocorre no limite de Wannier (n-> ?). Nesta situação o elétron iônico se encontra ao longo do eixo z para a simetria 3 P° e perpendicular ao eixo z para a simetria 1 P°. Esse fenômeno é causado pela interação elétron-elétronIn this work we describe the concepts of aligrnment and orientation based on the formalism of Fano and Macek formalism and we study the photoionization of the Helium atom ground state. We have used an approximate wave function obtained from the diagonalization of the Gailitis- Damburg operator. The anisotropy of the system formed after the colision was measured through the calculation of the ion electronic density and also by the use of the alignment tensor and orientation vector. The behaviour of these parameters for the transitions np ->1s and n ->n-1 as a function of n (the principal quantum number of the ion) was plotted for both the relevant symmetries, 1 P° and 3 P°. We have observed that the maximum alignment of the system, with respect to the dominant symmetry axis defined as the z axis, occurs in the Wannier threshold (n->?). This leads to the alignment of the ionic electron along the z axis for the 3 P°symmetry, and orthogonal to the z axis for the 1P° symmetry. This phenomenom is caused by the electron-electron Ínteraction.
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Limburg, Johannes. "Hollow-atom probing of surfaces". [S.l. : [Groningen] : s.n.] ; [University Library Groningen] [Host], 1996. http://irs.ub.rug.nl/ppn/152208046.
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Power, William. "Dynamics of laser-atom interactions". Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294807.
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D'Arcy, Michael Brendan. "Quantum chaos in atom optics". Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249527.
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Östersjö, Victor. "Supersymmetry for the Hydrogen Atom". Thesis, Karlstads universitet, Institutionen för ingenjörsvetenskap och fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-35397.
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In this thesis it will be shown that the hydrogen atom has a SU(2) × SU(2) symmetry generated by the quantum mechanical angular momentum and Runge-Lenz vector operators. Additionally, the hydrogenic atom will be studied with supersymmetric methods to identify a supersymmetry that relates different such systems. This thesis is intended to present the material in a manner accessible to people without background in Lie groups and supersymmetry, as well as fill in some calculations between steps that are not spelt out in the litterature.
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McMahon, S. J. "Heavy Atom Radiotherapy Dose Enhancement". Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527871.
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Huang, C. "Atom diffractometry from nanostructured surfaces". Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604697.
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Chapter 1 introduces the basic principles of atom diffractometry and scattering from surfaces. I discuss the experimental and theoretical methods employed to determine the atom-surface interaction potential. In addition, a brief description of the apparatus and typical measurements are given. In Chapter 2, a new method is developed for determining the atom-surface interaction potential by interference effects. Based on a 0.5 ML Ni-Cu(100) surface, the helium interaction potential on an unreconstructed Ni(100) overlayer is determined experimentally, which would not have been previously possible due to the absence of diffractive and resonant scattering intensity. A detailed investigation of growth mechanism and surface structure of Ni-Cu(100) is presented in Chapter 3. It is observed that the nickel growth occurs by forming ordered overlayer structures at and below room-temperature, whilst proceeds via alloying processes at high temperatures. The second growth system, Li-Cu(100), is studied in Chapter 4. A sequence of ordered overlayer structures with unusual electronic corrugations are observed in the growth at low temperatures. The surface corrugation for helium scattering from a complex structure, c(5V 2 x v 2)R45° Li-Cu (100), is derived through a diffraction analysis using the exact, close-coupled channels method. Finally, a comparison between neon and helium scattering from an ordered c(2x2) Li-Cu(100) structure is presented in Chapter 5. The surface corrugation for neon scattering is determined on a metallic overlayer for the first time. it is found that the neon corrugation amplitude is at least one order of magnitude larger than for helium. Such a difference exceeds those observed previously on low-index transition metal surfaces.
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Glass, John T. "Relativistic ion-atom collision processes". Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282153.
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O'Rouke, Sheelagh Francesca Camille. "Theory of ion-atom collisions". Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334486.
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McSherry, D. M. "Ionization in ion-atom collisions". Thesis, Queen's University Belfast, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368567.
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Torabi-Goudar, Firuz Andreas. "Techniques for cold atom manipulation". Thesis, University of Strathclyde, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288735.
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