Dissertationen: „Electron pairs“

1

Carpenter, Joanna Katharine Hicks. „Magnetic field effects on electron transfer reactions in photosynthetic bacteria“. Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390466.

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2

Giebels, Franz-Josef [Verfasser], und Roland [Akademischer Betreuer] Feder. „Emission of electron-electron and electron-positron pairs from solid surfaces due to electron or positron impact / Franz-Josef Giebels. Betreuer: Roland Feder“. Duisburg, 2015. http://d-nb.info/1075456193/34.

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3

Hencken, Kai. „Electromagnetic production of electron positron pairs in relativistic heavy ion collisions“. [S.l.] : [s.n.], 1994. http://edoc.unibas.ch/diss/DissB_3179.

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4

Marchant, Melanie Erin. „Bose-Einstein condensation of exotic electron pairs in the Extended Hubbard Model“. Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266974.

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5

Fursman, Catherine E. „Electron spin echo envelope modulation spectroscopy of radical pairs in photosynthetic bacteria“. Thesis, University of Oxford, 2000. http://ora.ox.ac.uk/objects/uuid:1ccaf0e5-3a45-4f13-a184-a4f1cf772c9b.

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Electron spin echo envelope modulation (ESEEM) spectroscopy is widely used to study the radical pairs created during the primary steps of photosynthesis. In this thesis the analysis of ESEEM spectra is improved, and some new applications and variations of this experiment suggested. Experimental spectra from species such as P⁺Q^-_A, the secondary radical pair formed in the reaction centre of the bacterium Rhodobacter sphaeroides, give information about the exchange and dipolar couplings between the radicals. The model used to analyse the data affects the results; this thesis suggests two improvements. First, the effect of anisotropic hyperfine couplings in the radicals is considered by the addition of a single spin-1/2 nucleus to the model. This approach suggests that previous models neglecting the effect of nuclei may have been slightly in error. Secondly, several model fittings are performed in the time domain. This approach avoids the Fourier transformation to the frequency domain so that experimental dead-time does not corrupt the data. An excellent fit to experimental data is found with a model containing one spin-1/2 nucleus on each radical. The hyperfine coupling parameters resulting from the fit are consistent with independent experimental results. Use is made of the method of Cramér-Rao lower bounds to assess the precision to which experimental parameters are determined from a time domain curve fitting. It is shown that the lower bounds may also be used to determine the optimum sampling strategy for the experiment. An example is given of the novel use of ESEEM to determine the distance between the radicals in the strongly coupled, uncorrelated radical pair Q^-_AQ^-_B ESEEM has not yet been used for this purpose, and the simulated spectra produced here indicate that the experiment could be used to evaluate the dipolar coupling and hence the inter-radical distance. This thesis considers the possibility of performing ESEEM at higher frequencies than are usually considered. Calculations show that the increased resolution of the g-tensors allow an experiment performed at the W-band frequency of 95 GHz to make a correlation between the relative orientations of the radicals and the dipolar axis, information which has previously been unavailable from a single experiment.

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6

Wechakama, Maneenate. „Multi-messenger constraints and pressure from dark matter annihilation into electron-positron pairs“. Phd thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2013/6740/.

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Despite striking evidence for the existence of dark matter from astrophysical observations, dark matter has still escaped any direct or indirect detection until today. Therefore a proof for its existence and the revelation of its nature belongs to one of the most intriguing challenges of nowadays cosmology and particle physics. The present work tries to investigate the nature of dark matter through indirect signatures from dark matter annihilation into electron-positron pairs in two different ways, pressure from dark matter annihilation and multi-messenger constraints on the dark matter annihilation cross-section. We focus on dark matter annihilation into electron-positron pairs and adopt a model-independent approach, where all the electrons and positrons are injected with the same initial energy E_0 ~ m_dm*c^2. The propagation of these particles is determined by solving the diffusion-loss equation, considering inverse Compton scattering, synchrotron radiation, Coulomb collisions, bremsstrahlung, and ionization. The first part of this work, focusing on pressure from dark matter annihilation, demonstrates that dark matter annihilation into electron-positron pairs may affect the observed rotation curve by a significant amount. The injection rate of this calculation is constrained by INTEGRAL, Fermi, and H.E.S.S. data. The pressure of the relativistic electron-positron gas is computed from the energy spectrum predicted by the diffusion-loss equation. For values of the gas density and magnetic field that are representative of the Milky Way, it is estimated that the pressure gradients are strong enough to balance gravity in the central parts if E_0 < 1 GeV. The exact value depends somewhat on the astrophysical parameters, and it changes dramatically with the slope of the dark matter density profile. For very steep slopes, as those expected from adiabatic contraction, the rotation curves of spiral galaxies would be affected on kiloparsec scales for most values of E_0. By comparing the predicted rotation curves with observations of dwarf and low surface brightness galaxies, we show that the pressure from dark matter annihilation may improve the agreement between theory and observations in some cases, but it also imposes severe constraints on the model parameters (most notably, the inner slope of the halo density profile, as well as the mass and the annihilation cross-section of dark matter particles into electron-positron pairs). In the second part, upper limits on the dark matter annihilation cross-section into electron-positron pairs are obtained by combining observed data at different wavelengths (from Haslam, WMAP, and Fermi all-sky intensity maps) with recent measurements of the electron and positron spectra in the solar neighbourhood by PAMELA, Fermi, and H.E.S.S.. We consider synchrotron emission in the radio and microwave bands, as well as inverse Compton scattering and final-state radiation at gamma-ray energies. For most values of the model parameters, the tightest constraints are imposed by the local positron spectrum and synchrotron emission from the central regions of the Galaxy. According to our results, the annihilation cross-section should not be higher than the canonical value for a thermal relic if the mass of the dark matter candidate is smaller than a few GeV. In addition, we also derive a stringent upper limit on the inner logarithmic slope α of the density profile of the Milky Way dark matter halo (α < 1 if m_dm < 5 GeV, α < 1.3 if m_dm < 100 GeV and α < 1.5 if m_dm < 2 TeV) assuming a dark matter annihilation cross-section into electron-positron pairs (σv) = 3*10^−26 cm^3 s^−1, as predicted for thermal relics from the big bang.
Trotz vieler Hinweise auf die Existenz von dunkler Materie durch astrophysikalische Beobachtungen hat sich die dunkle Materie bis heute einem direkten oder indirekten Nachweis entzogen. Daher gehrt der Nachweis ihrer Existenz und die Enthüllung ihrer Natur zu einem der faszinierensten Herausforderungen der heutigen Kosmologie und Teilchenphysik. Diese Arbeit versucht die Natur von dunkler Materie durch indirekte Signaturen von der Paarzerstrahlung dunkler Materie in Elektron-Positronpaare auf zwei verschiedene Weisen zu untersuchen, nämlich anhand des Drucks durch die Paarzerstrahlung dunkler Materie und durch Grenzen des Wirkungsquerschnitts für die Paarzerstrahlung dunkler Materie aus verschiedenen Beobachtungsbereichen. Wir konzentrieren uns dabei auf die Zerstrahlung dunkler Materie in Elektron-Positron-Paare und betrachten einen modellunabhängigen Fall, bei dem alle Elektronen und Positronen mit der gleichen Anfangsenergie E_0 ~ m_dm*c^2 injiziert werden. Die Fortbewegung dieser Teilchen wird dabei bestimmt durch die Lösung der Diffusions-Verlust-Gleichung unter Berücksichtigung von inverser Compton-Streuung, Synchrotronstrahlung, Coulomb-Streuung, Bremsstrahlung und Ionisation. Der erste Teil dieser Arbeit zeigt, dass die Zerstrahlung dunkler Materie in Elektron-Positron-Paare die gemessene Rotationskurve signifikant beeinflussen kann. Die Produktionsrate ist dabei durch Daten von INTEGRAL, Fermi und H.E.S.S. begrenzt. Der Druck des relativistischen Elektron-Positron Gases wird aus dem Energiespektrum errechnet, welches durch die Diffusions-Verlust-Gleichung bestimmt ist. Für Werte der Gasdichte und des magnetischen Feldes, welche für unsere Galaxie repräsentativ sind, lässt sich abschätzen, dass für E_0 < 1 GeV die Druckgradienten stark genug sind, um Gravitationskräfte auszugleichen. Die genauen Werte hängen von den verwendeten astrophysikalischen Parametern ab, und sie ändern sich stark mit dem Anstieg des dunklen Materie-Profils. Für sehr große Anstiege, wie sie für adiabatische Kontraktion erwartet werden, werden die Rotationskurven von Spiralgalaxien auf Skalen von einegen Kiloparsek für die meisten Werte von E_0 beeinflusst. Durch Vergleich der erwarteten Rotationskurven mit Beobachtungen von Zwerggalaxien und Galaxien geringer Oberflächentemperatur zeigen wir, dass der Druck von Zerstrahlung dunkler Materie die Übereinstimmung von Theorie und Beobachtung in einigen Fällen verbessern kann. Aber daraus resultieren auch starke Grenzen für die Modellparameter - vor allem für den inneren Anstieg des Halo-Dichteprofils, sowie die Masse und den Wirkungsquerschnitt der dunklen Materie-Teilchen. Im zweiten Teil werden obere Grenzen für die Wirkungsquerschnitte der Zerstrahlung der dunkler Materie in Elektron-Positron-Paare erhalten, indem die beobachteten Daten bei unterschiedlichen Wellenlängen (von Haslam, WMAP und Fermi) mit aktuellen Messungen von Elektron-Positron Spektren in der solaren Nachbarschaft durch PAMELA, Fermi und H.E.S.S. kombiniert werden. Wir betrachten Synchrotronemission bei Radiound Mikrowellenfrequenzen, sowie inverse Compton-Streuung und Final-State-Strahlung bei Energien im Bereich der Gamma-Strahlung. Für die meisten Werte der Modellparameter werden die stärksten Schranken durch das lokale Positron-Spektrum und die Synchrotronemission im Zentrum unser Galaxie bestimmt. Nach diesen Ergebnissen sollte der Wirkungsquerschnitt für die Paarzerstrahlung nicht größer als der kanonische Wert für thermische Relikte sein, wenn die Masse der dunklen Materie-Kandidaten kleiner als einige GeV ist. Zusätzlich leiten wir eine obere Grenze für den inneren logarithmische Anstieg α des Dichteprofiles des dunklen Materie Halos unserer Galaxie ab.

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7

Glendinning, I. „A study of inclusive lepton pairs in multihadronic events from electron positron annihilation at PETRA“. Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377472.

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8

Reis, Thomas. „Search for new massive resonances decaying to dielectrons or electron-muon pairs with the CMS detector“. Doctoral thesis, Universite Libre de Bruxelles, 2015. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209131.

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Le sujet de cette thèse porte sur la recherche de nouvelles résonances massives se désintégrant en une paire d’électrons ou une paire électron-muon avec le détecteur CMS, installé auprès du Grand Collisionneur du Hadrons (LHC) au CERN. Les données analysées correspondent à l’ensemble des collisions proton-proton enregistrées par le détecteur en 2012 à une énergie dans le centre de masse de 8 TeV. Après une brève introduction au modèle standard des particules élémentaires et à quelques unes des théories allant au-delà, le LHC et le détecteur CMS sont présentés. La reconstruction des différentes particules créées lors des collisions, en particulier des électrons et muons de haute énergie, est ensuite discutée. Deux analyses séparées sont menées.

La première consiste en la recherche d’une nouvelle résonance étroite, plus massive que le boson Z, dans le spectre de masse invariante des paires d’électrons, dont la principale contribution, dans le modèle standard, provient du processus de Drell–Yan. De telles résonances sont notamment prédites par des modèles dits de grande unification ou à dimensions spatiales supplémentaires. Le bruit de fond provenant des processus du modèle standard étant réduit dans la région étudiée, quelques événements localisés peuvent suffire pour mener à une découverte, et la sélection des électrons est optimisée afin de ne perdre aussi peu d’événements que possible. Les différentes contributions des bruits de fond sont partiellement estimées à partir de simulations. Une méthode basée sur le spectre de masse invariante des paires électron-muon mesuré dans les données est développée pour valider la contribution du second bruit de fond en terme d’importance. Aucun excès n’est observé par rapport aux prédictions du modèle standard et des limites supérieures à 95% de niveau de confiance sont placées sur le rapport entre la section efficace de production multipliée par le rapport de branchement d’une nouvelle résonance et celle au pic du boson Z. Ces limites sont ensuite converties en limites inférieures sur la masse de différentes particules hypothétiques de spin 1 ou de spin 2.

La seconde analyse consiste en une recherche de résonances massives et étroites dans le spectre de masse invariante des paires électron-muon. De telles résonances briseraient la conservation du nombre leptonique tel que prédit par le modèle standard. Cette possibilité existe cependant dans certains modèles de nouvelle physique. C’est notamment le cas pour un modèle à dimensions supplémentaires où apparaissent des nouveaux bosons neutres lourds. La sélection des événements demande un électron de haute énergie comme dans l’analyse précédente, et un muon de grande impulsion transverse. La stratégie de recherche est similaire au cas des paires d’électrons :le fait de rechercher un signal étroit rend l’analyse statistique très peu sensible aux erreurs systématiques affectant la normalisation absolue du spectre de masse électron-muon. Comme aucune déviation significative n’est observée par rapport aux prévisions du modèle standard, des limites supérieures sur la section efficace multipliée par le rapport de branchement sont établies pour le modèle à dimensions spatiales supplémentaires. Étant données les faibles valeurs théoriques de la section efficace de production des résonances violant la conservation de la saveur dans ce modèle, la quantité de données analysées ne permet pas d’en déduire une limite inférieure sur leur masse. Cette analyse représente néanmoins la première recherche directe avec l’expérience CMS, de bosons massifs, se désintégrant avec violation du nombre leptonique, en une paire électron-muon.

Doctorat en Sciences
info:eu-repo/semantics/nonPublished

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9

Asano, Yasuhiro, Yuki Sawa, Yukio Tanaka und Alexander A. Golubov. „Odd-frequency pairs and Josephson current through a strong ferromagnet“. American Physical Society, 2007. http://hdl.handle.net/2237/11285.

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10

[Verfasser], Maneenate Wechakama, und Matthias [Akademischer Betreuer] Steinmetz. „Multi-messenger constraints and pressure from dark matter annihilation into electron-positron pairs / Maneenate Wechakama. Betreuer: Matthias Steinmetz“. Potsdam : Universitätsbibliothek der Universität Potsdam, 2013. http://d-nb.info/1041521669/34.

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11

Paudel, Hari. „The effect of electron-hole pairs in semiconductor and topological insulator nanostructures on plasmon resonances and photon polarizations“. Doctoral diss., University of Central Florida, 2014. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6338.

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The generation of electron-hole pairs in materials has great importance. In direct bandgap semiconductor materials, the mechanism of radiative recombination of electron-hole pairs leads to the emission of photons, which is the basis of Light Emitting Diodes (LEDs). The excitation of electron-hole pairs by absorption of photons is the active process in photodiodes, solar cells, and other semiconductor photodetector devices. In optoelectronic devices such as optical switches which are based on transmission and reflection of the photons, electron-hole pairs excitation is a key for the device performance. Diodes and transistors are also great discoveries in electronics which rely on the generation and recombination of electron-hole pairs at p-n junctions. In three-dimensional topological insulators (3D TIs) materials nanostructures excitation of electron-hole pairs can be utilized for the quantum memory, quantum information and quantum teleportation. In two-dimensional (2D) layered materials like graphene, MoS2, MoSe2, WS2 and WSe2 generation and recombination of electron hole pairs is main process at p-n junctions, infrared detectors and sensors. This PhD thesis is concerned with the physics of different types of electron-hole pairs in various materials, such as wide-bandgap semiconductors, 3D topological insulators, and plasmonic excitations in metallic nanostructures. The materials of interest are wide bandgap semiconductors such as TiO2 , 3D TIs such as Pb1-xSnxTe and the 2D layered materials such as MoS2 and MoO3. We study the electronic and optical properties in bulk and nanostructures and find applications in the area of semiclassical and quantum information processing. One of the interesting applications we focus in this thesis is shift in surface plasmon resonance due to reduction in index of refraction of surrounding dielectric environment which in turns shifts the wavelength of surface plasmon resonance up to 125 nm for carrier density of 10^22/cm^3. Employing this effect, we present a model of a light controlled plasmon switching using a hybrid metal-dielectric heterostructures. In 3D TIs nanostructures, the time reversible spin partners in the valence and conduction band can be coupled by a left and a right handed circular polarization of the light. Such coupling of light with electron-hole pair polarization provides an unique opportunity to utilize 3D TIs in quantum information processing and spintronics devices. We present a model of a 3D TI quantum dot made of spherical core-bulk heterostructure. When a 3D TI QD is embedded inside a cavity, the single-photon Faraday rotation provides the possibility to implement optically mediated quantum teleportation and quantum information processing with 3D TI QDs, where the qubit is defined by either an electron-hole pair, a single electron spin, or a single hole spin in a 3D TI QD. Due to excellent transport properties in single and multiple layers of 2D layered materials, several efforts have demonstrated the possibility to engineer electronic and optoelectronic devices based on MoS2. In this thesis, we focus on theoretical and experimental study of electrical property and photoluminescence tuning, both in a single-layer of MoS2.We present theoretical analysis of experimental results from the point of view of stability of MoO3 defects in MoS2 single layer and bandstructures calculation. In experiment, the electrical property of a single layer of MoS2 can be tuned from semiconducting to insulating regime via controlled exposure to oxygen plasma. The quenching of photoluminescence of a single sheet of MoS2 has also been observed upon exposure to oxygen plasmas. We calculate the direct to indirect band gap transitions by going from MoS2 single sheet to MoO3 single sheet during the plasma exposure, which is due to the formation of MoO3 rich defect domains inside a MoS2 sheet.
Ph.D.
Doctorate
Physics
Sciences
Physics

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12

Boţan, Vitalie. „Bose-Einstein Condensation of Magnetic Excitons in Semiconductor Quantum Wells“. Doctoral thesis, Uppsala University, Department of Physics, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7112.

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In this thesis regimes of quantum degeneracy of electrons and holes in semiconductor quantum wells in a strong magnetic field are studied theoretically. The coherent pairing of electrons and holes results in the formation of Bose-Einstein condensate of magnetic excitons in a single-particle state with wave vector K. We show that correlation effects due to coherent excitations drastically change the properties of excitonic gas, making possible the formation of a novel metastable state of dielectric liquid phase with positive compressibility consisting of condensed magnetoexcitons with finite momentum. On the other hand, virtual transitions to excited Landau levels cause a repulsive interaction between excitons with zero momentum, and the ground state of the system in this case is a Bose condensed gas of weakly repulsive excitons. We introduce explicitly the damping rate of the exciton level and show that three different phases can be realized in a single quantum well depending on the exciton density: excitonic dielectric liquid surrounded by weakly interacting gas of condensed excitons versus metallic electron-hole liquid. In the double quantum well system the phase transition from the excitonic dielectric liquid phase to the crystalline state of electrons and holes is predicted with the increase of the interwell separation and damping rate.

We used a framework of Green's function to investigate the collective elementary excitations of the system in the presence of Bose-Einstein condensate, introducing "anomalous" two-particle Green's functions and symmetry breaking terms into the Hamiltonian. The analytical solution of secular equation was obtained in the Hartree-Fock approximation and energy spectra were calculated. The Coulomb interactions in the system results in a multiple-branch structure of the collective excitations energy spectrum. Systematic classification of the branches is proposed, and the condition of the stability of the condensed excitonic phase is discussed.

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13

Göringer, Christian [Verfasser]. „Search for high mass resonances decaying into electron-positron pairs in proton-proton collisions at √(s) = 7 TeV with the ATLAS detector [[Elektronische Ressource]] / Christian Göringer“. Mainz : Universitätsbibliothek Mainz, 2013. http://d-nb.info/1034583670/34.

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14

Nowocin, John Kendall. „Kerr electro-optic measurements for electric field and space charge distributions using similar and dissimilar electrode pairs“. Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82400.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 97).
The electrical breakdown strength of insulating materials is a major limiting factor of reliability in electric power, medical devices, and other high electric field applications. Electrical breakdown strength increase results in increased reliability and energy storage in high voltage capacitors and other devices. If a correlation can be found between the breakdown strength and the electric field distribution when a voltage is applied without electrical breakdown, then this may be a critical step toward non-destructive electrical breakdown tests. The generation and transport of space charge in high voltage stressed dielectric liquids are not well understood or controlled. Electric field distributions, distorted by space charge, cannot be calculated from knowledge of the electrode configuration, dielectric properties, and source excitation alone. In this work, the Kerr effect, an electro-optic method based on field-induced birefringence, is used to measure the electric field and space charge distributions between a pair of high voltage stressed identical or different metal electrodes. The non-uniformities in the electric field can then be mapped to determine the shape of space charge distortion of the electric field distribution for each electrode pair configuration. A large well monitored Kerr cell was built to replace a previously used small Kerr cell, and incorporated many improvements to the systems measurement accuracy and repeatability. The electrode pairs were combinations of similar and dissimilar metals. The similar electrode pairs provided double checks of the testing process with the voltage polarity reversed. Software was written to automate the testing process and collect data for processing. Pre and post processing code was written to determine statistics for data analysis.
by John Kendall Nowocin.
S.M.

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15

König, Sebastian [Verfasser]. „Measurement of the forward-backward asymmetry of Z boson decays in electron-positron pairs with the ATLAS detector in proton-proton collisions at root out s = 7TeV at the LHC / Sebastian König“. Mainz : Universitätsbibliothek Mainz, 2014. http://d-nb.info/1047689995/34.

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16

Libby, James Frederick. „The study of e'+e'-#->##mu#'+#mu#'-(#gamma#) and the measurement of trilinear gauge couplings at LEP2 using the DELPHI detector“. Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301903.

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17

Moscoso, Michael Douglas. „Electron-positron pair winds /“. Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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18

Blinne, Alexander [Verfasser], Holger [Gutachter] Gies, Burkhard [Gutachter] Kämpfer und Antony [Gutachter] Ilderton. „Electron positron pair production in strong electric fields / Alexander Blinne ; Gutachter: Holger Gies, Burkhard Kämpfer, Antony Ilderton“. Jena : Friedrich-Schiller-Universität Jena, 2017. http://d-nb.info/1177602954/34.

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19

Nahn, Steven C. (Steven Christopher) 1968. „Pair production of W bosons in electron positron annihilation“. Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50334.

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20

Adamczyk, Katrin. „Ultrafast charge transfer processes in solution“. Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2010. http://dx.doi.org/10.18452/16202.

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Die Reaktionspfade und Reaktionsdynamik photoinduzierter bimolekularer Ladungstransferreaktionen werden mit Hilfe der ultraschnellen polarisationsabhängigen UV-Pump/IR-Probe-Spektroskopie charakterisiert. Allgemein akzeptierte Modelle zur Beschreibung von bimolekularen Elektrontranserreaktionen nehmen an, dass Ladungstrennung in polaren Lösungsmitteln zu zwei Arten von Ionenpaaren führt, den lockeren (LIPs) und den engen Ionenpaaren (TIPs). TIPs und LIPs können durch die Beobachtung von Schwingungsmoden spektroskopisch unterschieden werden. Allerdings deuten die multiplen Zeitskalen sowohl für die Bildung von TIPs als auch LIPs darauf hin, dass eine Unterscheidung in zwei Arten von Ionenpaaren mit definierter Geometrie eine erhebliche Vereinfachung ist. TIPs und LIPs sind vielmehr als Grenzfälle zu betrachten, zwischen derer eine kontinuierliche Verteilung verschiedener Ionenpaare existiert. Die Natur der Ionenpaare wird durch die Verteilung der neutralen Reaktionspaare vor Initiation der Reaktion bestimmt. Außerdem wird gezeigt, dass TIPs höchst anisotrop sind. Die Wichtigkeit der beidseitigen Orientierung der Reaktanten wird dabei offengelegt. Weiterhin wird erstmalig ein femtosekundenspektroskopischer Beweis für die Existenz von Kohlensäure in wäßriger Lösung präsentiert. Eine Photosäure wurde verwendet, um die ultraschnelle Protonierung von Bikarbonat optisch auszulösen. Kohlensäure wurde bisher als Feststoff in Eismatrizen und in der Gasphase detektiert. Da Kohlensäure als Intermediat zwischen Kohlenstoffdioxid und Bikarbonat postuliert wird, ist ihre Charakterisierung von immenser Bedeutung für das Verständnis grundlegender Säure-Base Chemie von Karbonaten in wäßriger Lösung. Die Analyse der zeitabhängigen Signale unter Verwendung eines theoretischen Modells erlaubt die Bestimmung der bimolekularen Reaktionsdynamik. Dies ermöglicht einen Einblick in die Säure-Base Chemie von Kohlensäure.
The reaction pathways and dynamics of photoinduced bimolecular charge transfer reactions are characterised with ultrafast polarisation-sensitive UV-pump/IR-probe-spectroscopy. Generally accepted models for bimolecular electron transfer reactions suppose that charge separation in polar solvents leads to two geminate ion pairs, namely loose (LIPs) and tight ion pairs (TIPs). By monitoring vibrational marker modes TIPs and LIPs can be distinguished spectroscopically. However, multiple time scales for the formation of TIPs and LIPs indicate that a distinction between two kinds of ion pairs with well-defined geometries is a considerable simplification. TIPs and LIPs should rather be regarded as limiting cases, as there is a continuous distribution of different ion pairs between these two limits. The crucial parameter governing the nature of the ion pairs is the distribution of neutral reaction pairs subsequent to initiation of the reaction. Furthermore, TIPs are found to be highly anisotropic, revealing the importance of mutual orientation of the reactants. This thesis also presents for the first time femtosecond infrared spectroscopic results proving the existence of carbonic acid in aqueous solution. A photoacid is used to optically trigger the ultrafast protonation of bicarbonate. Carbonic acid has only been detected as solid existing in ice matrices and in the gas phase, so far. Because carbonic acid is often postulated as intermediate between carbon dioxide and bicarbonate its characterisation is of substantial support in understanding fundamental acid-base chemistry of carbonates in aqueous solution as well as in biophysical situations. Analysing the time-dependent signals using a theoretical model to describe bimolecular reaction dynamics an on-contact proton transfer reaction rate is derived. This gives an insight into the acid-base chemistry of carbonic acid.

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21

Damjanović, Sanja. „Electron pair production in Pb-Au collisions at 40 AGeV“. [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965148920.

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22

Hu, Yuan Zheng. „Theory of electron-hole pair excitations in semiconductor quantum dots“. Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/185516.

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This dissertation considers one- and two-electron-hole-pair excitations in ideally spherical semiconductor quantum dots with infinite or finite confinement potentials. The optical absorption edge of the semiconductor micsrocrystallites is found to be higher than that in the corresponding bulk semiconductor. This blue shift is approximately proportional to 1/R², where R is the radius of the semiconductor microspheres. For small quantum dots with infinite confinement potential, the energies and wave-functions of quantum confined excitons and biexcitons are computed using a numerical matrix diagonalization method. Both numerical matrix digaonalization and perturbative calculations prove that the binding energy of biexcitons is strictly positive regardless of material parameters. A general formula for the optical susceptibility of quantum dots is derived, from which, optical spectra are computed. The theoretical results qualitatively agree with recent experimental observations. Some novel optical properties of quantum dots are revealed by this study, such as the existence of excited biexciton states energetically above the exciton ground state resonance and modified optical nonlinearities. Extending our numerical scheme, we compute the effects of impurities or crystal defects in a simple model. The calculation shows that charge defects or impurities have only a small influence on the optical spectra of quantum dots. The details of the quantum confinement conditions, such as the finite value of the quantum confinement potential and different electron-hole masses inside and outside the dot, are studied within the framework of the variational scheme. Finally, we extend the numerical matrix diagonalization method to investigate the valence band coupling effect in quantum dots by including the Luttinger Hamiltonian. It is found that the concept of heavy- and light-hole has to be modified to describe the hole states in semiconductor quantum dots. Also, the valence band mixing due to spin-orbit interaction changes significantly the optical selection rules and consequently influences the allowed optical excitations in quantum dots.

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Zenker, Bernd [Verfasser]. „Electron-hole pair condensation at the semimetal-semiconductor transition / Bernd Zenker“. Greifswald : Universitätsbibliothek Greifswald, 2014. http://d-nb.info/1051797799/34.

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24

Brinne, Roos Johanna. „Electron Recombination with Small Molecular Ions“. Licentiate thesis, Stockholm : Bioteknologi, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4375.

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25

Norlin, Nils. „Extended Förster Theory of Electronic Energy Transport within Pairs of Reorienting Chromophoric Molecules“. Doctoral thesis, Umeå universitet, Kemi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-22471.

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An extended Förster theory (EFT), previously derived (L. B.-Å. Johansson et al. J. Chem. Phys., 1996,105) has theoretically been adapted and used in simulations of donor-acceptor energy transfer (DAET), which is a process often referred to as FRET. It was shown that the classical Förster theory is only valid in the initial part of the fluorescence decay. In this thesis an EFT is derived and outlined for electronic energy transport between two fluorescent molecules which are chemically identical, but photophysically non-identical. The energy migration within such asymmetric pairs is partially reversible and therefore referred to as partial donor-donor energy migration (PDDEM). The previously derived model of PDDEM (S. V. Kalinin et al. Spectrochim Acta Part A, 2002,58) is an approximation of the EFT. In particular, the EFT accounts for the time-dependent reorientations as well as the distance that influence the rate of electronic energy migration. The reorientation of the fluorophores transition dipole moments has been simulated using Brownian dynamics. As a result, the related “k2-problem” has been solved. The EFT of PDDEM has also been studied regarding the effect of PDDEM on experimental observables e.g. quantum yield of fluorescence and steady-state anisotropies

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Norlin, Nils. „Extended Förster theory of electronic energy transport within pairs of reorienting chromophoric molecules /“. Umeå : Department of Chemistry, Umeå University, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-22471.

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27

Schumann, Frank O. [Verfasser], J. [Akademischer Betreuer] Kirschner, W. [Akademischer Betreuer] Widdra und C. [Akademischer Betreuer] Back. „Studying the electron-electron correlation by pair emission from surfaces / Frank O. Schumann. Betreuer: J. Kirschner ; W. Widdra ; C. Back“. Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2012. http://d-nb.info/1025351878/34.

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28

Vampa, Giulio. „Role of Electron-Hole Recollisions in High Harmonic Generation from Bulk Crystals“. Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34935.

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When intense laser pulses interact with an atomic or solid target, high order harmonics of the fundamental laser frequency are generated. In the case of atoms, this highly nonlinear optical process is initiated by ionization and terminated by the energetic recollision and recombination of the ionized electron with its correlated ion. In this thesis I demonstrate, both theoretically and experimentally, that high harmonics from bulk crystals can originate from the recollision of electrons with their associated holes, similarly to the atomic case, but where ionization is replaced by excitation of electron-hole pairs that accelerate within the material. This model is first derived from a quantum-mechanical theory of the solid-laser interaction, and then confirmed experimentally in ZnO and Si crystals. Despite the link I establish between high harmonic generation in solids and gases, there are notable dissimilarities. These include: a generalized motion of electrons and holes in their respective bands and its consequences, a more prominent role of dephasing and enhanced sensitivity to perturbing fields. These aspects are investigated throughout this thesis. Finally, I develop a method that exploits the recollision mechanism to reconstruct the momentum-dependent band structure of solids.

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Tanaka, Yukio, Yasuhiro Asano und Alexander A. Golubov. „Shape of Cooper pairs in a normal-metal/superconductor junction“. American Physical Society, 2008. http://hdl.handle.net/2237/11296.

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30

Kalinin, Stanislav. „Electronic Energy Transfer within Asymmetric Pairs of Fluorophores: Partial Donor-Donor Energy Migration (PDDEM)“. Doctoral thesis, Umeå : Univ, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-338.

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31

Sabin, Julien. „Stabilité, dispersion, et création de paires pour certains systèmes quantiques infinis“. Phd thesis, Université de Cergy Pontoise, 2013. http://tel.archives-ouvertes.fr/tel-00924084.

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Cette thèse est consacrée à l'étude mathématique des propriétés de stabilité de systèmes quantiques infinis, décrits par des modèles non linéaires. Dans les chapitres 1 et 2, on étudie l'instabilité du vide relativiste menant au phénomène de création de paires électron-positron. Dans le chapitre 3, on considère la dynamique de ce même vide relativiste couplé à un champ scalaire. Les chapitres 4 et 5 sont consacrés au caractère dispersif de la dynamique non linéaire de Hartree pour des perturbations de la mer de Fermi, et en particulier à sa stabilité orbitale et asymptotique. Enfin, le chapitre 6 introduit une notion générale d'entropie relative entre deux états comportant une infinité de particules.

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Simkins, Luke. „Investigating electronic traps with a single cooper pair transistor“. Thesis, Royal Holloway, University of London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538304.

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33

Bjerwe, Ida. „Automatic Alignment Detection and Correction in Infrared and Visual Image Pairs“. Thesis, Linköpings universitet, Datorseende, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-165887.

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Previously well aligned image sensors, mounted on the same camera, might become misaligned depending on external vibrations. It is of interest to be able to automatically detect and correct for this misalignment, and to separate the deviation into pointing- and/or parallax errors. Two methods were evaluated for this purpose, an area based image registration method and a feature based image registration method. In the area based method normalized cross-correlation was used to estimate translation parameters. In the feature based method, SIFT or LIOP descriptors were used to extract features that were matched between the two image modalities to estimate transformation parameters. In both methods only image points that were in focus were extracted to avoid detection of false alignment deviations. The results indicate that the area based image registration method has potential to automatically detect and correct for an alignment deviation. Moreover, the area based method showed potential to separate the deviation into pointing errors and parallax errors. The feature based method was limited to specific scenes but could be used as a complement to the area based method in order to additionally correct for rotation and/or scaling.

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Parkes, Christopher John. „A determination of the W boson mass near the W-pair production threshold“. Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390501.

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35

Ro, Youngju. „Molecular complexes for artificial photosynthesis“. Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS412/document.

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Le développement de sources d’énergie renouvelables telles que les combustibles solaires est une question cruciale dans le contexte actuel du réchauffement de la planète. L'eau est une source abondante, respectueuse de l'environnement, bon marché et abondante en électrons et en protons nécessaires à la production de combustible. Par conséquent, l'oxydation de l'eau activée par la lumière est une étape clé de la photosynthèse artificielle et le développement de catalyseurs efficaces, robustes et durables constitue un objectif important pour les chimistes. Dans la première partie de cette étude, nous nous concentrons sur le développement de tels catalyseurs basés sur des complexes métalliques à base de métaux de la première série des éléments de transition tel que le cuivre pour cette étude. L'électrocatalyse et la photocatalyse par oxydation de l'eau ont été étudiées. La deuxième partie du travail concerne la formation de paires d'ions entre les espèces à double charge opposée du catalyseur complexe et de l'accepteur d'électrons et du photosensibilisant et du catalyseur complexe. Cette étude devrait apporter des preuves solides de l'influence de chaque composant du photosystème par l'association et la dissociation de paires d'ions.Dans la troisième partie, nous étudions un système synthétique sensibilisant-catalyseur capable de photoactiver une molécule d’eau liée à l’unité catalytique par le biais d’une oxydation à deux électrons et à deux protons, réalisant toute la caractérisation photophysique de la dyade. Par conséquent, l’étude des complexes moléculaires pour la photosynthèse artificielle fournit diverses orientations pour développer le rendement d’utilisation de l’énergie solaire
Development of renewable energy sources like solar fuels is a crucial issue in the actual context of global warming. Water is an environmentally friendly, cheap and abundant source of the electrons and protons needed for fuel production. Therefore, light-activated water oxidation is a key step in artificial photosynthesis and the development of efficient, robust and sustainable catalysts is an important goal for chemists. In the first part of this study, we focus on the development of such catalysts based on earth abundant copper complexes. The water oxidation electrocatalysis and photocatalysis were investigated. The second part of the work concerns the ion pair formation between the oppositely double charged species of complex catalyst and electron acceptor and Photosensitizer and complex catalyst are investigated. This study should bring solid evidence on the influence of each component in photosystem through the ion pair association and dissociation. In the third part, we study a synthetic sensitizer-catalyst system that can photoactivate a water molecule bound to the catalytic unit through a two-electron, two-proton abstraction, performed all the photophysical characterization of the dyad. Therefore, studying molecular complexes for artificial photosynthesis provides diverse direction to develop the utilization efficiency of solar energy

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Evans, David Lewis. „Studies of electrons in the CMS detector and a proposed search for high invariant mass e⁺e⁻ pairs“. Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.702122.

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The Standard Model of particle physics is extremely well tested and yet is not believed to be a theory of everything. Many extensions of the Standard Model predict the existence of new particles. The Large Hadron Collider (LHC) is a high energy proton-proton collider which may be able to produce such particles. The Compact Muon Solenoid (CMS) experiment, a general purpose detector designed to measure the results of high energy proton-proton collisions at the LHC is described. In this work strategies have been developed to search for new physics by identifying high energy electrons produced by the decay of new particles. Detailed simulation programs have been used to test methods which may be used to identify events containing high energy electrons and record these for later study. The efficiency to record events containing an electron and a positron from the decay of a new particle with a mass of 1 Te V was improved from 70% to 99%. A new algorithm, which more robustly measures electron energy, was studied. Techniques to measure the performance of the criteria used to select events of particular interest have been studied, in addition to the level of contamination that may be present due to erroneously selected events. Using the methods developed, it has been shown that CMS could discover new particles that decay to electron-positron pairs up to a mass of 1.65 TeV using only 100 pb-1 of data. Models predicting spin-1 Z' particles and spin-2 Randall Sundrum gravitons have been considered and methods that could be used in early data to distinguish between these models have been investigated

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BRAMBILLA, GABRIELE. „ELECTRON POSITRON PAIR FLOW AND CURRENT COMPOSITION IN THE PULSAR MAGNETOSPHERE: STEPS TOWARD SELF-CONSISTENCY“. Doctoral thesis, Università degli Studi di Milano, 2018. http://hdl.handle.net/2434/546452.

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We performed ab-initio Particle-In-Cell (PIC) simulations of a pulsar magnetosphere. We injected particles in two ways: everywhere and only near to the star surface. Then we study how the magnetosphere transitions from the vacuum to a nearly force-free configuration. We compare the injection from the surface force-free like configuration with ones obtained in a PIC simulation where particles are injected everywhere as well as with macroscopic force-free simulations. We found that although both PIC solutions have similar structure of electromagnetic fields and current density distributions, they have different particle density distribution. In fact in the injection from the surface solution, electrons and positrons counterstream only along parts of the return current regions and most of the particles leave the magnetosphere without returning to the star. We also found that pair production in the outer magnetosphere is not critical for filling the whole magnetosphere with plasma. We study how the current density distribution supporting the global electromagnetic configuration is formed by analyzing particle trajectories. We found that electrons precipitate to the return current layer inside the light cylinder and positrons precipitate to the current sheet outside the light cylinder by crossing magnetic field lines contributing to the charge density distribution required by the global electrodynamics. Moreover, there is a population of electrons trapped in the region close to the Y-point. On the other hand the most energetic positrons are accelerated close to the Y-point. These processes can have observational signatures that, with further modeling efforts, would help to distinguish this particular magnetosphere configuration from others.

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Muscenti, Thomas Michael. „Density Functional Theory Study of Rutile SiO₂ Stishovite: An Electron Pair Description of Bulk and Surface Properties“. Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/10179.

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The bulk structure and the nonpolar, stoichiometric (110) surface of stishovite, rutile structure type SiO₂, has been studied using a first principles, density functional method. The geometric and electronic structure, including the density of states, charge density, and electron localization function for both the bulk and the surface have been examined. The electron pair properties of both bulk and surface-layer atoms were found to be similar to molecular analogs. The analogs allowed for the description of surface electronic structure using simple molecular models. The adsorption of hydrogen fluoride was studied on the (110) surface. The geometry optimized and electronic structure have been found for various initial geometries. Relaxed structures of certain initial geometries give dissociated hydrogen fluoride upon geometry optimization.
Master of Science

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39

Jewsbury, P. J. „The electronic structure of the ion pair states of molecular iodine“. Thesis, University of Edinburgh, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.653008.

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The electronic configurations of molecular states of iodine are studied through the Optical-Optical Double Resonance excitation of the ion pair states in low vibrational levels. The two photon OODR excitation of ungerade IP states from the gerade ground state is rationalised and the strength of u/g coupling at the intermediate step interpreted in terms of a hyperfine interaction first described by Broyer et al. The potential function of the cl_g(ab) gerade coupling partner in the hyperfine Hamiltonian is derived, along with the lowest levels of a new IP state in the second cluster, H1_u(2) state. An OODR excitation scheme for populating the 0^-_u(2) IP state is proposed and the dominant component of the c1_g(ab) state configuration is found for R ≈ 5.5AA. The radiative lifetimes of nine IP states in low vibrational levels are determined and combined with the relative fluorescent intensities of the IP→Valence charge transfer transitions to derive the Einstein A-coefficients for all the strong transitions from these IP states. A theoretical model is developed in terms of a separated atom description for the electronic configurations of these states and is used to predict the relative dipole strengths of the IP→Valence transitions. The Einstein A-coefficients are then interpreted to give the electronic configurations of the IP states around R^IP_e and the relative strengths of the transition dipoles for pigma͍p_{igma and p}_π͍p_π electron transfer between ionic centres. A significant difference from the free ion configurations is found with the lowest energy IP states of a given symmetry adopting as low a p_igma occupancy at the cationic centre as the inter-electron repulsion and spin-orbit energies will allow. This stabilisation is driven by the field gradient due to the anionic charge.

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Jeanne, Matthieu. „Paris, un enjeu capital : rivalités de pouvoirs et stratégies d'acteurs pour le contrôle politique et l'aménagement de Paris“. Thesis, Paris 8, 2015. http://www.theses.fr/2015PA080051/document.

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L’élection du socialiste Bertrand Delanoë en 2001 à la mairie de Paris marque une rupture majeure dans l’histoire de la capitale : Paris n’est plus le bastion du conservatisme qu’elle fut au XXe siècle. Dans le même temps, la ville connaît de profonds bouleversements sociologiques et démographiques : elle cesse de perdre des habitants, rajeunit et s’embourgeoise.L’analyse géopolitique s’avère féconde pour analyser ces mutations inédites. En effet, depuis 1977, le pouvoir municipal parisien, qui représente une position de pouvoir unique en France, est l’objet d’intenses rivalités. Longtemps ignorées dans le champ de la géographie et des sciences politiques, celles-ci constituent, pourtant, un facteur explicatif essentiel des dynamiques politiques et urbaines. Cette thèse ambitionne de les analyser. Elle s’appuie à la fois sur un riche corpus de données électorales, et sur des enquêtes de terrain menées dans l’Est parisien et dans le 16e arrondissement.Dans un premier temps, cette thèse montre que l’alternance politique de 2001 ne résulte pas de clefs d’analyse simples : le mouvement de gentrification, les divisions de la droite parisienne ou le contexte politique national. Elle analyse les stratégies territorialisées des acteurs politiques qui constituent de puissants systèmes géopolitiques locaux.Dans un second temps, cette thèse met en valeur les enjeux géopolitiques de l’aménagement de la capitale. Les politiques publiques d’aménagement occupent désormais une place centrale dans les stratégies électorales de l’ensemble des acteurs politiques. Tout comme leur contestation, qui donne lieu à des conflits d’aménagement locaux qui fragilisent le pouvoir municipal parisien
The election of the socialist Bertrand Delanoë as mayor of Paris in 2001 marks a major turning point in the history of the capital: Paris is no longer the bastion of conservatism it was throughout the twentieth century. At the same time, the city is undergoing profound sociological and demographic changes: the capital continues to lose people, while rejuvenating and undergoing gentrification.A geopolitical analysis is fruitful when it comes to studying these unprecedented changes. Since 1977, the Parisian municipal authority, which is in a unique position of power in France, has been the subject of intense rivalries. Long ignored in the field of geography and political science, these rivalries are, however, a key factor in explaining policy and urban dynamics. This thesis intends to analyze them. It relies both on a rich body of electoral data, and on field surveys carried out in neighborhoods of eastern Paris and in the 16th arrondissement.Firstly, this thesis shows that the political change in 2001 was not the result of one single factor: the movement towards gentrification, divisions in the Parisian right or the national political context. In order to highlight what makes Parisian municipal elections unique, it is more appropriate to analyze the strategies of the key political players that focus on specific local issues. These are at the heart of local geopolitical systems.Secondly, this thesis highlights the geopolitical issues of the development of the capital. Public planning policies now occupy a central place in the electoral strategies of all political players. As does opposition to them, resulting in local planning disputes that undermine Parisian municipal power

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Bouchiat, Vincent. „Fluctuations quantiques de la charge dans les circuits a un electron et a une paire de cooper“. Paris 6, 1997. http://www.theses.fr/1997PA066241.

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Dans des circuits constituees d'electrodes metalliques sub-microniques de petite capacite c, separees par des jonctions tunnel, le transfert controle d'electrons individuels par effet tunnel peut etre realise : la charge des electrodes y est alors quantifiee en multiple d'electrons. L'operation de tels circuits <<<>a un electron<>>> necessite d'une part que l'energie caracteristique des fluctuations thermiques k#bt reste petite devant l'energie electrostatique des electrodes e#2/2c, et d'autre part que les resistances des jonctions soient grandes devant le quantum de resistance h/e#2. Quel est le processus de disparition des effets mono-electron lorsque les resistances tunnel sont sous en dessous de cette limite ? que devient cette limite lorsque les electrodes sont supraconductrices ? qu'elle est alors l'influence de la dissipation sur le comportement quantique de ces systemes ? cette these apporte des reponses experimentales a ses questions. Dans un transistor a un electron, circuit elementaire de la monoelectronique utilise en electrometrie, la conductance aux faibles tensions est modulee par la charge de la tension de grille avec une periode de un electron. A temperature donnee, l'amplitude de cette modulation diminue fortement lorsque la resistance des jonctions diminue sous le seuil h/e#2 : l'energie electrostatique est attenuee par les fluctuations quantiques de la charge et les effets a un electron repousses aux plus basses temperatures. L'experience de boite a paire de cooper, constituee d'une electrode supraconductrice couplee a un reservoir par une jonction josephson, permet de tester la generalisation des effets de charges aux supraconducteurs. Lorsque les paires de cooper sont stockees dans la boite, le couplage josephson induit des fluctuations quantiques qui detruisent partiellement la quantification de la charge de l'electrode et instaurent un etat de coherence quantique macroscopique. Ces fluctuations quantiques peuvent a leur tour etre detruites par la dissipation. Le bruit dans ces systemes ainsi que des procedes originaux pour leur nanofabrication sont enfin presentes.

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Sanchez, Carlos Alberto. „Towards single shot measurements of a Cooper pair box qubit using an rf single electron transistor“. College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/3203.

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Thesis (Ph. D.) -- University of Maryland, College Park, 2005.
Thesis research directed by: Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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Orakzai, Muazzam W. „Ion pair production and electron loss of fluorine and chlorine atom collisons with rare gas targets“. Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5184.

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44

Mizielinski, Matthew. „A theory of electron-hole pair excitation in the adsorption of simple atoms on metal surfaces“. Thesis, University of Bath, 2007. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436869.

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Recent experiments have provided direct evidence for the excitation of electronhole pairs during the adsorption of atoms on metal surfaces. The excitation of electron-hole pairs is an inherently non-adiabatic process which is often ignored in standard theoretical treatments of surface phenomena, using tools such as density functional theory (DFT), as the Born-Oppenheimer approximation cannot be used. To obtain a theoretical model for the electronic excitation process it is therefore necessary to go beyond conventional methods. Previous theoretical descriptions have used a nearly-adiabatic approximation to describe electronic excitations. However, these methods have been found to fail in situations where an adsorbing atom undergoes a transition between a spin-polarised and unpolarised state. In this thesis we develop a fully non-adiabatic theory using a simple description of the adsorbate-metal interaction; the time-dependent, mean-field Newns- Anderson model. This model describes a simple electronic system in which a band of metal states interacts with a single atomic orbital, which can undergo a ‘spin-transition’. We derive expressions describing the time-dependent transfer of charge and energy between the adsorbate and surface, as well as the spectrum of electronic excitations generated. Each of these results describe the evolution of the electronic system in terms of a simple set of parameters. These results are demonstrated using a set of example parameter variations to explore the impact of variables such as adsorbate speed and the temperature of the system. A set of parameter variations describing the interaction of hydrogen isotopes with copper and silver surfaces are obtained from DFT calculations. These parameters are used to drive our model through a single approach of the adsorbate to the surface. We find the results of these calculations to be in good agreement with reported experimental results. Our conclusions, and some possible directions for further work, are summarised in the final chapter.

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Li, Qi. „A pair of stationary stochastic processes with application to Wichita temperature data“. Thesis, Wichita State University, 2010. http://hdl.handle.net/10057/3644.

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The thesis investigates a pair of stationary stochastic process models whose domains are the set of integers and the set of real numbers respectively. The stationary processes with our specific correlation functions include the discrete and continuous first and second order autoregressive processes as their special cases. The maximum likelihood method is then applied to obtain the nonlinear equation system for the maximum likelihood estimators of the model parameters and the solutions are found by using the deepest gradient algorithm. The advantage of the algorithm lies in the calculation could be divided into several steps at a cost of O(n) calculations per step. Finally, predictions are given for both simulated data and Wichita temperature data.
Thesis (M.S.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Mathematics and Statistics
This research is supported in part by the Kansas NSF EPSCoR under Grant EPS 0903806 and in part by a Kansas Technology Enterprize Corporation grant on Understanding Climate Change in the Great Plains: Source, Impact, and Mitigation.

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Xia, You. „Experiments on EHD injection, interaction and electrocoalescence of water droplet pairs in oil“. Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI039/document.

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Lorsque des champs électriques sont appliqués à des mélanges eau-huile, les petites gouttelettes d'eau sont attirées entre elles et se regroupent en gouttes plus grosses. Ce processus d’électrocoalescence rend plus efficace la séparation huile-eau par sédimentation.Des données expérimentales sur l’électrocoalescence de très petites gouttelettes sont nécessaires pour améliorer la compréhension de la dynamique de l'interface eau-huile et pour valider les modèles numériques. La configuration simple étudiée dans ce travail de thèse concerne une petite paire de gouttelettes tombant dans une cuve d'huile modèle et soumise à un champ électrique aligné avec l’axe de symétrie des gouttes et la gravité.La première partie du travail a consisté à générer de façon contrôlée d’une paire de très petites gouttelettes (dans la gamme de diamètres 20-200 microns) alignée avec le champ électrique. La génération de goutte à la demande, par méthode éléctrohydrodynamique (EHD) a été améliorée pour un meilleur contrôle du diamètre et de la charge électrique des gouttelettes injectées à partir d'une aiguille métallique unique. Ceci a été obtenu en appliquant à un ménisque d'eau pendant à l’extrémité de l’aiguille des impulsions électriques de forme optimisée.La caractérisation électrique et hydrodynamique des paires de gouttelettes et leur coalescence sont alors principalement déduites de l'analyse des vitesses de chute, avec et sans application d’un champ électrique à courant continu. Des données complètes de positions des gouttelettes et de leur vitesse en fonction du temps sont déduites de prises de vues vidéo. Une attention particulière a été accordée aux visualisations de très petites gouttelettes tombant à petites vitesses, associant des angles multiples de prise de vue, de forts zooms et des vidéos à grande vitesse.La modélisation des différents termes d'interactions hydrodynamiques et électrostatiques entre les gouttelettes permet de déduire des vitesses enregistrées leur masse charge électrique respectives. Quand se produit une coalescence des deux gouttelettes, un enregistrement de la vitesse de la gouttelette résultante, avec et sans tension électrique appliquée, permet de contrôler la conservation de la masse et de la charge électrique, et la validation du procédé.Un premier ensemble de données est constitué d'environ 70 cas différents, avec différentes paire des gouttelettes (dans une plage de diamètre limitée de façon à ce que les vitesses de chute soient comprises entre 0,1 et 0,3 mm/s) et en faisant varier la tension appliquée à courant continu ou alternatif. L'analyse des résultats et des incertitudes expérimentales et un exemple de comparaison possible avec des simulations numériques utilisant le logiciel Comsol Multiphysics ™, permettent d'effectuer des recommandations pour les travaux futurs.Ce travail a été financé par le projet “Fundamental understanding of electrocoalescence in heavy crude oils”; coordonné par SINTEF Energy Research. Le projet a été soutenu par The Research Council of Norway, dans le cadre du contrat n °: 206976 / E30, et par les partenaires industriels suivants: Wärtsilä Oil & Gas Systems AS, Petrobras et Statoil ASA
When electric fields are applied in oil-water mixtures small water droplets are attracted to others and merge in larger drops. This electrocoalescence process makes more efficient the oil-water separation by sedimentation.Experimental data on the electrocoalescence of very small droplets will be useful to improve the understanding of the dynamics of water-oil interface and to validate numerical models. The simple configuration studied consists in a small droplet pair falling in stagnant model oil, under electric field aligned with the symmetry axis of the droplet pair and the direction of gravity.First part of the work consisted in the well-controlled generation of very small droplet pair (range 20-200 microns) aligned with electric field. Droplet-on-Demand generation by EHD method was improved for a better control of the diameter and electric charge of droplets injected from a single metallic needle. This was obtained by applying to a pendant water meniscus optimized multistage high voltage electric pulses.Electrical and hydrodynamic characterization of the droplet pairs and their coalescence are then mainly deduced from the analysis of falling velocities, with and without applied DC electric field. A complete data set of droplet position and velocity is deduced from video. A special attention was paid to the visualizations of very small droplet and small falling velocities, involving multiple angle of view, strong zooming and high speed video.Modelling the different terms of hydrodynamic and electrostatic interactions between droplets allows deducing from the recorded velocities their respective mass and electric charge. When coalescence occurs, a record of the resulting single droplet velocity, with and without applied voltage, allows controlling the mass and charge conservations and validating the method.A first data set was constituted of about 70 different cases, with varying droplets pair (with a limited diameter range to remain with falling velocities between 0.1 and 0.3 mm/s) and varying applied DC or AC voltage. Analyses of the results and experimental uncertainties, and example of possible comparison with numerical simulations using Comsol Multiphysics™ software, allow performing some recommendations for future work.This work was funded by the project “Fundamental understanding of electrocoalescence in heavy crude oils”; co-ordinated by SINTEF Energy Research. The project was supported by The Research Council of Norway, under the contract no: 206976/E30, and by the following industrial partners: Wärtsilä Oil & Gas Systems AS, Petrobras and Statoil ASA

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Li, Changhui [Verfasser], J. [Akademischer Betreuer] Kirschner, H. [Akademischer Betreuer] Winter und Wolf [Akademischer Betreuer] Widdra. „Electron pair emission from surfaces upon He2+ impact / Changhui Li. Betreuer: J. Kirschner ; H. Winter ; Wolf Widdra“. Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2014. http://d-nb.info/1063331633/34.

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Behnke, Lucie [Verfasser], Jürgen [Akademischer Betreuer] Kirschner, Wolf [Akademischer Betreuer] Widdra und Markus [Akademischer Betreuer] Donath. „Electron pair emission from NiO and metal surfaces / Lucie Behnke. Betreuer: Jürgen Kirschner ; Wolf Widdra ; Markus Donath“. Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2014. http://d-nb.info/1058587145/34.

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Ngetich, Geoffrey. „The defect level of carbon vacancy carbon antisite pair in 4H-SiC photo induced electron paramagnetic resonance“. Birmingham, Ala. : University of Alabama at Birmingham, 2008. https://www.mhsl.uab.edu/dt/2008m/ngetich.pdf.

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Ardolino, Kyle R. „Semi-supervised learning of bitmask pairs for an anomaly-based intrusion detection system“. Diss., Online access via UMI:, 2008.

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Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Electrical Engineering, 2008.
Includes bibliographical references.

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