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1
Palmer, R. E. "Inelastic electron scattering by physisorbed molecules." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383837.
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Eggeling, Joachim. "Inelastic electron scattering from adsorbate covered semiconductor surfaces." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313773.
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Couto, Rafael Carvalho. "Coupled electron-nuclear dynamics in inelastic X-ray scattering." Universidade Federal de Goiás, 2016. http://repositorio.bc.ufg.br/tede/handle/tede/7510.
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Esta tese dedicada a estudos tericos e experimentais de espalhamento ressonante inelstico de raios-X (Resonant inelastic X-ray scattering - RIXS) de molculas de monxido de carbono e gua em fase gasosa. Usando estado da arte clculos ab initio de estrutura eletrnica e formalismo de pacotes de onda dependente do tempo, uma anlise completa dos espectros RIXS experimental dos dois sistemas moleculares foi realizada. Na anlise do CO RIXS, fomos capazes de reproduzir o experimento RIXS com excelente preciso, permitindo uma descrio completa dos espectros experimentais. Interferncia entre diferentes canais RIXS correspondentes disperso via orbitais moleculares ortogonais no estado excitado do CO descrito. Com a ajuda do espectro de alta resoluo e simulaes ab initio, mostramos a quebra da aproximao de Born-Oppenheimer na regio onde estados nais de Rydberg acoplam com o estado nal de valncia. Explicamos a formao de uma caracterstica espectral, que foi atribuda a um nico estado em estudos anteriores. Alm disso, atravs da combinao experimento-teoria, aprimoramos o mnimo do potencial do estado excitado de valncia E 1 , juntamente com o constante de acoplamento entre o estado de valncia e dois estados de Rydberg. A m de estudar a gua, desenvolvemos uma nova abordagem terica para descrever molculas triatmicas atravs do formalismo de propagao de pacote de ondas, que reproduz com grande preciso a estrutura vibracional os espectros experimentais RIXS de alta resoluo, permitindo obter importantes concluses. Ns demonstramos que, devido ao acoplamento dos modos vibracionais e anarmonicidade do potencial no estado fundamental e das superfcies de energia potencial do estados excitados, diferentes estados excitados de camada interna em RIXS podem ser usados como portas para sondar diferentes dinmicas de vibrao e para mapear o potencial do estado fundamental usando modos normais de vibrao molecular. O ajuste dos raios-X acima da ressonncia de absoro permite extrair informaes adicionais sobre o potencial do estado fundamental, devido alta excitao vibracional. Substituio isotpica investigada por meio de simulaes tericas e as importantes caractersticas da dinmica nuclear so discutidas, especialmente para o estado excitado de camada interna dissociativo, onde um chamado pico \atmico " formado. Este recurso crucial para explicar a dinmica nuclear em RIXS da gua. Mostramos o forte potencial de experimentos RIXS de alta resoluo combinados IV com simulaes tericas de alto nvel para estudos avanados de estados moleculares altamente excitados, bem como superfcies de energia potencial do estado fundamental, send utilizada como uma tcnica auxiliar para espectroscopia ptica e infra vermelho.
This Thesis is devoted to theoretical and experimental studies of resonant inelastic X-ray scattering (RIXS) of gas-phase carbon monoxide and water molecules. Using state-of-the-art ab initio electronic structure calculations and a time-dependent wave packet formalism, we make a complete analysis of the experimental RIXS spectra of the two molecular systems. In the CO RIXS analysis, we are able to reproduce the RIXS experiment with an excellent accuracy, allowing for a complete description of all experimental features. Interference between di erent RIXS channels corresponding to the scattering via orthogonal molecular orbitals in the core-excited state of CO is described. With the help of the high-resolution spectrum and extensive ab initio simulations we show the complete breakdown of the Born- Oppenheimer approximation in the region where forbidden nal Rydberg states are mixed with a valence allowed nal state. Here we explain the formation of a spectral feature which was attributed to a single state in previous studies. Moreover, through an experimentaltheoretical combination, we improve the minimum of the valence E 1 excited state, along with the coupling constant between the valence and two Rydberg states. In order to study the water system, we developed a new theoretical approach to describe triatomic molecules through the wave packet propagation formalism, which reproduces with high accuracy the vibrational structure of the high-resolution experimental quasi-elastic RIXS spectra, allowing to draw several important conclusions. We demonstrate that due to the vibrational mode coupling and anharmonicity of the ground and core-excited potential energy surfaces, di erent core-excited states in RIXS can be used as gates to probe di erent vibrational dynamics and to map the ground state potential using molecular vibrational normal modes. Tuning the X-rays above the absorption resonance allows to extract additional information about the ground state potential, due to high vibrational excitation. Isotopic substitution is investigated by theoretical simulations and important dynamical features are discussed, especially for the dissociative core-excited state, where a so-called \atomic" peak is formed. This feature is crucial to explain the nuclear dynamics in RIXS from water. We show the strong potential of high-resolution RIXS experiments combined with high-level theoretical simulations for advanced studies of highly excited molecular states, as well as of ground state potential energy surfaces, as an auxiliary technique to optical and IR spectroscopy.
4
Timbrell, P. Y. "An electron energy loss spectrometer for studies of adsorption on Pd(111)." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384528.
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Mowrey, Richard Carlton. "Theoretical studies of inelastic molecule-surface and resonant electron-atom and electron-molecule scattering /." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu148725958026243.
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Moreno, Carrascosa Andrés. "Theory of elastic and inelastic X-ray scattering." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31442.
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X-rays have been widely exploited to unravel the structure of matter since their discovery in 1895. Nowadays, with the emergence of new X-ray sources with higher intensity and very short pulse duration, notably X-ray Free Electron Lasers, the number of experiments that may be considered in the X-ray regime has increased dramatically, making the characterization of gas phase atoms and molecules in space and time possible. This thesis explores in the theoretical analysis and calculation of X-ray scattering atoms and molecules, far beyond the independent atom model. Amethod to calculate inelastic X-ray scattering from atoms and molecules is presented. The method utilizes electronic wavefunctions calculated using ab-initio electronic structure methods. Wavefunctions expressed in Gaussian type orbitals allow for efficient calculations based on analytical Fourier transforms of the electron density and overlap integrals. The method is validated by extensive calculations of inelastic cross-sections in H, He+, He, Ne, C, Na and N2. The calculated cross-sections are compared to cross-sections from inelastic X-ray scattering experiments, electron energy-loss spectroscopy, and theoretical reference values. We then begin to account for the effect of nuclear motion, in the first instance by predicting elastic X-ray scattering from state-selected molecules. We find strong signatures corresponding to the specific vibrational and rotational state of (polyatomic) molecules. The ultimate goal of this thesis is to study atomic and molecular wavepackets using time-resolved X-ray scattering. We present a theoretical framework based on quantum electrodynamics and explore various elastic and inelastic limits of the scattering expressions. We then explore X-ray scattering from electronic wavepackets, following on from work by other groups, and finally examine the time-resolved X-ray scattering from non-adiabatic electronic-nuclear wavepackets in the H2 molecule, demonstrating the importance of accounting for the inelastic effects.
7
Slaughter, Daniel Stephen, and d. slaughter@aip org au. "Superelastic Electron Scattering from Caesium." Flinders University. Chemistry Physics and Earth Sciences, 2007. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20071009.100421.
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This thesis describes an experimental study of superelastic electron scattering from
the 6^2P_3/2
state of caesium. The present status of electron-atom collision studies is
initially reviewed and the motivation behind the current work is then presented. A
description of the theoretical framework is subsequently provided in the context of
the present experimental study, followed by an overview of the several theoretical
approaches for describing electron-atom interactions which are currently available.
The apparatus and experimental setup used throughout the project are also described
in detail. Technical specifications and data are provided, including diagrams (where
appropriate) for a laser frequency locking system, electron gun and spectrometer,
atomic beam source and data acquisition system. The experimental procedures are
explained and discussed, including a detailed analysis of the optical pumping
process required to excite the atomic target. A substantial component of this project
was to address several potential sources of systematic error and to reduce these
wherever possible. All of the errors and uncertainties relevant to the experiment are
discussed in chapter 5.
In chapter 6 the results of the present superelastic electron scattering experiments are
reported for incident electron energies of 5.5eV, 8.5eV and 13.5eV, corresponding
to superelastic electron energies of 7eV, 10eV and 15eV. These results are presented
as three reduced Stokes parameters, P1, P2, P3 and a coherence parameter, P+ . For
comparison, predictions from a number of currently available theories are presented alongside the experimental results. Finally, conclusions are drawn on this work in the context of the current status of electron-atom scattering from alkali-metals.
8
Evans, Alan Charles. "The study of condensed matter by deep inelastic neutron scattering." Thesis, University of Warwick, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387343.
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Kula, Mathias. "Elastic and Inelastic Electron Tunneling in Molecular Devices." Licentiate thesis, Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3958.
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Womersley, Lindsay Adele. "Preliminary analysis of neutral current deep inelastic electron-proton scattering at HERA." Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240757.
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Dowd, James Franklyn. "Probe of Electroweak Interference Effects in Non-Resonant Inelastic Electron-Proton Scattering." W&M ScholarWorks, 2018. https://scholarworks.wm.edu/etd/1550153997.
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The Qweak collaboration at Jefferson Lab made the first direct measurement of the proton's weak charge, Q_W^p, via a measurement of the parity-violating asymmetry in elastic e ⃑p scattering with low four-momentum transfer. to meet the high-precision goals, energy-dependent electroweak radiative corrections were applied to the measured asymmetry. The γZ box, □_γZ, where a photon and a Z-boson are simultaneously exchanged, was the most problematic of these corrections. It could not be calculated through the same perturbative methods as the rest of the corrections. The □_γZ correction depends on theoretical models of the γZ interference structure functions, F_1,2^γZ, for which there are almost no data. Presented in this dissertation are the results from a specialized run of the Qweak experiment. Using the Qweak apparatus, with modifications, a measurement of the parity-violating asymmetry of non-resonant inelastic e ⃑p scattering was made with 3.35 GeV incident electrons. The apparatus was tuned to inelastic e ⃑p scattering with an average W=2.33 GeV and Q^2=0.082 GeV^2, in order to test the theoretical models used to predict the □_γZ radiative correction. The final inelastic asymmetry, after correcting for beam polarization and backgrounds, was found to be A_phys= -13.5±4.4 ppm, in agreement with theoretical predictions. This measurement provides important experimental validation of the theoretical methods used to calculate the □_γZ radiative correction. Additionally, this measurement provides useful experimental constraints on the F_1,2^γZ interference structure functions used in those theoretical models.
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Adloff, Catherine. "Open charm production in deep inelastic electron proton scattering with the H1 detector at HERA." Wuppertal : Bergische Univ., Fachbereich Physik, 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=964180596.
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Blankenship, Thomas Keith. "Rapidity gap in the final state hadron distribution in deep inelastic electron scattering at HERA." Diss., This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-06062008-170753/.
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Lee, Zhongbo [Verfasser]. "Incorporate elastic and inelastic scattering into image calculation for low-voltage transmission electron microscope / Zhongbo Lee." Ulm : Universität Ulm. Fakultät für Naturwissenschaften, 2014. http://d-nb.info/1049987411/34.
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Ebert, Tania. "Hadronic energy flow in deep inelastic electron-proton scattering and proton structure at low Bjorken x." Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260304.
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Geondzhian, Andrey. "Resonant inelastic X-ray scattering as a probe of exciton-phonon coupling." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAY077/document.
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Les phonons contribuent à la diffusion inélastique résonante des rayons X (RIXS) du fait du couplage entre les degrés de liberté électronique et ceux du réseau. Contrairement à d'autres techniques sensibles aux interactions électron-phonon, la technique RIXS peut donner accès aux constantes de couplage dépendantes du moment. Des informations sur la dispersion de l'interaction électron-phonon sont très précieuses dans le contexte de la supraconductivité anisotrope conventionnelle et non conventionnelle.Nous avons considéré la contribution des phonons sur la diffusion RIXS d’un point de vue théorique. Contrairement aux études précédentes nous soulignons le rôle du couplage du réseau avec les trous de cœur. Notre modèle, avec les paramètres obtenus ab-initio, montre que même dans le cas d'un trou de coeur profond, la technique RIXS sonde le couplage exciton-phonon plutôt qu’un couplage direct électron-phonon.Cette différence conduit à des écarts quantitatifs et qualitatifs pour le couplage électron-phonon implicite par rapport à l'interprétation standard dans la littérature. Ainsi, notre objectif est de développer une approche rigoureuse pour quantifier le couplage électron-phonon dans le contexte des mesures de diffusion RIXS. La possibilité de reproduire avec précision les résultats expérimentaux à partir des calculs ab-initio, sans recourir à des paramètres ajustés, doit être considérée comme le test ultime d'une compréhension correcte de la contribution des phonons sur la diffusion RIXS.Nous commençons notre travail en considérant uniquement l’interaction trou de coeur-phonon dans le contexte de la spectroscopie par photoémission de rayons X. Nous combinons un calcul ab-initio de la fonction de réponse en espace réel avec des techniques de fonctions de Green à plusieurs corps pour reproduire les bandes latérales vibrationnelles dans les molécules SiX4 (X = H, F). L'approche que nous avons développée peut être appliquée aux matériaux cristallins.Nous examinons ensuite la contribution des phonons aux spectres d'absorption des rayons X. Contrairement aux excitations chargées générées par la photoémission par rayons X, l'absorption des rayons X crée une excitation neutre que nous approchons en tant que trou de cœur et électron excité. Nous résolvons d’abord la partie électronique du problème au niveau de l’équation de Bethe-Salpeter, puis nous habillons la quasi-particule excitonique à 2 particules résultante avec les interactions exciton-phonon en utilisant l’Ansatz des cumulants. La viabilité de cette méthode a été testée en calculant le seuil K XAS de la molécule N2 et le seuil K d’Oxygène de l’acétone. Les spectres vibrationnels obtenus concordent avec les résultats expérimentaux.Enfin, nous construisons une formulation hybride de la section transversale RIXS qui préserve la sommation explicite sur un petit nombre d'états finals, mais remplace la sommation sur les états intermédiaires, ce qui pourrait être extrêmement coûteux, par une fonction de Green. Nous avons obtenu un développement de la fonction de Green et dérivé des solutions analytiques exactes (dans la limite de non-recul) et approximatives. Le formalisme a de nouveau été testé sur le seuil K de l'acétone et est bien en accord avec l'expérience. En perspectives des travaux futurs, nous discutons de l’applicabilité de notre formalisme aux matériaux cristallinsPhonons contribute to resonant inelastic X-ray scattering (RIXS) as a consequence of the coupling between electronic and lattice degrees of freedom. Unlike other techniques that are sensitive to electron-phonon interactions, RIXS can give access to momentum dependent coupling constants. Information about the dispersion of the electron-phonon interaction is highly desirable in the context of understanding anisotropic conventional and unconventional superconductivity.We considered the phonon contribution to RIXS from the theoretical point of view. In contrast to previous studies, we emphasize the role of the core-hole lattice coupling. Our model, with parameters obtained from first principles, shows that even in the case of a deep core-hole, RIXS probes exciton-phonon coupling rather than a direct electron-phonon coupling.This difference leads to quantitative and qualitative deviations from the interpretation of the implied electron-phonon coupling from the standard view expressed in the literature. Thus, our objective is to develop a rigorous approach to quantify electron-phonon coupling within the context of RIXS measurements. The ability to accurately reproduce experimental results from first-principles calculations, without recourse to adjustable parameters, should be viewed as the ultimate test of a proper understanding of the phonon contribution to RIXS.We start by considering only the core-hole--phonon interaction within the context of X-ray photoemission spectroscopy. We combine an ab initio calculation of the real-space response function with many-body Green's functions techniques to reproduce the vibrational side-bands in SiX4 (X=H, F) molecules. The approach we developed is suitable for application to crystalline materials.We next consider the phonon contribution to X-ray absorption spectra. Unlike the charged excitations generated by X-ray photoemission, X-ray absorption creates a neutral excitation that we approximate as a core-hole and an excited electron. We first solved the electronic part of the problem on the level of the Bethe-Salpeter equation and then dressed the resulting 2-particle excitonic quasiparticle with the exciton-phonon interactions using the cumulant ansatz. The viability of this methodology was tested by calculating the N K-edge XAS of the N2 molecule and the O K-edge of acetone. The resulting vibronic spectra agreed favorably with experimental results.Finally, we construct a hybrid formulation of the RIXS cross section that preserves explicit summation over a small number of final states, but replaces the summation over intermediate states, which might be enormously expensive, with a Green's function. We develop an expansion of the Green's function and derive both analytically exact (in the no-recoil limit) and approximate solutions. The formalism was again tested on the O K-edge of acetone and agrees well with the experiment. To provide an outlook towards future work, we discuss application of the developed formalism to crystalline materials
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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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Catterall, Corinna. "Hadronic final states in deep inelastic electron-proton scattering at a centre of mass energy of 300 GeV." Thesis, University College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336330.
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Donovan, Keith Thomas. "Hadronic fragmentation studies in ep scattering at HERA." Thesis, Queen Mary, University of London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312965.
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Adloff, Catherine [Verfasser]. "Open charm production in deep inelastic electron proton scattering with the H1 detector at HERA / vorgelegt von Catherine Adloff." Wuppertal : Bergische Univ., Fachbereich Physik, 2001. http://d-nb.info/964180596/34.
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Capuano, Carissa Lee. "Parity-violating asymmetry in the nucleon to delta transition: A Study of Inelastic Electron Scattering in the G0 Experiment." W&M ScholarWorks, 2012. https://scholarworks.wm.edu/etd/1539623595.
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The parity-violating asymmetry arising from inelastic electron scattering at backward angle (∼ 95??) near the Delta resonance has been measured for both hydrogen and deuterium targets as part of the G 0 experiment. For Q2 = 0.34 (GeV/c) 2 and W = 1.18 GeV, the asymmetries were found to be AHinel=-33.4+/-5 .3stat+/-5 .1sysppm, ADinel=-43.6+/-1 4.6stat+/- 6.2sysppm. .;From the hydrogen asymmetry, the axial transition form factor, GAND , can be extracted. GAND is related to probability of the quark spin-flip that occurs as the proton transitions to the Delta. From the measured asymmetry, the form factor is found to be GAND=-0.046+/- 0.35stat+/- 0.34sys+/- 0.06theory. .;Though GAND has been previously studied using charged current reactions, the G0 measurement represents the first measurement of the asymmetry in the neutral weak sector. These findings agree within errors with the theoretical predictions.
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Mafra, Daniela Lopes. "Using inelastic scattering of light to understand the nature of electron-phonon interactions and phonon self-energy renormalizations in graphene materials." Universidade Federal de Minas Gerais, 2012. http://hdl.handle.net/1843/MPDZ-8Y4GEG.
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In the last decade, many theoretical and experimental achievements have been made in the physics of graphene. In particular, Raman spectroscopy has been playing an important role in unraveling the properties of graphene systems. In this thesis we use the Raman spectroscopy to study some effects of the electron-phonon coupling in monolayer and bilayer graphene and to probe the electronic and vibrational structure of bilayer graphene. Phonon self-energy corrections have mostly been studied theoretically and experimentally for phonon modes with zone-center (q = 0) wavevectors. Here, we combine Raman spectroscopy and gate voltage to study phonons of monolayer graphene for the features originated from a double-resonant Raman (DRR) process with q .= 0 wavevectors. We observe phonon renormalization effects in which there is a softening of the frequency and a broadening of the decay width with increasing the gate voltage, that is opposite from what is observed for the zone-center q = 0 case. We show that this renormalization is a signature for the phonons with q . 2k wavevector that come from both intravalley and intervalley DRR processes. Within this framework, we resolve the identification of the phonon modes contributing to the G. Raman feature, at ¡ 2450 cm.1, and also for
five second order Raman combination modes in the frequency range of 1700 . 2300 cm.1 of monolayer graphene. By combining the DRR theory with the anomalous phonon renormalization effect, we show a new technique for using Raman spectroscopy to identify the proper phonon mode assignment for each combination mode. We also study the behavior of the optical phonon modes in bilayer graphene devices
by applying top gate voltage, using Raman scattering. We observe the splitting of the Raman G band as we tune the Fermi level of the sample, which is explained in terms of mixing of the Raman (Eg) and infrared (Eu) phonon modes, due to different doping in the two layers. We show that the comparison between the experiment and theoretical model not only gives information about the total charge concentration in the bilayer graphene device, but also allows to separately quantify the amount of unintentional charge coming from the top and the bottom of the system, and therefore to characterize the intrinsic charges of bilayer graphene with its surrounding environment. In the second part of this thesis, the dispersion of electrons and phonons near the K point of bilayer graphene was investigated in a resonant Raman study of the G¡Ç band using different laser excitation energies in the near-infrared and visible range.
The electronic structure was analyzed within the tight-binding approximation, and the Slonczewski-Weiss-McClure (SWM) parameters were obtained from the analysis of the dispersive behavior of the G¡Ç band considering both the inner and the outer DRR processes. We show that the SWM parameters obtained considering the inner process are in better agreement with those obtained from other experimental techniques, strongly suggesting that the inner process is the main responsible for the G¡Ç feature in graphene. Additionally, the dependence of the intensity of the four peaks that compose the G¡Ç band of bilayer graphene with laser excitation energy and laser power is explored and explained in terms of the electron-phonon coupling and the relaxation of the photon-excited electron. We show that the carrier relaxation occurs predominantly by emitting a lowenergy acoustic phonon and the different combinations of relaxation processes determine the relative intensities of the four peaks that give rise to the G¡Ç band. Some peaks show an increase of their intensity at the expense of others, thereby making the intensity of the peaks both different from each other and dependent on laser excitation energy and on power level. This effect gives important information about the electron and phonon dynamics and needs to be taken into account for certain applications of bilayer graphene in the field of nanotechnology.Na última década, muitos avanços teóricos e experimentais foram alcançados na física do grafeno. Em particular, a Espectroscopia Raman tem sido muito importante para elucidar propriedades físicas e químicas em sistemas de grafeno. Nessa tese nós usamos a Espectroscopia Raman para estudar alguns dos efeitos do acoplamento elétron-fônon no grafeno de camada única e de dupla camada e para obter informações sobre a estrutura eletrônica e vibracional do grafeno de camada dupla. As renormalizações das energias dos fônons tem sido estudadas basicamente para fônons com vetor de onda nulo (q=0). Aqui, nós combinamos a Espectroscopia Raman com aplicação de tensão de porta, para estudar, em grafeno de camada única, as bandas originadas do processo Raman com dupla ressonância (DDR) com etores de onda q0. Nós observamos os efeitos de decaimento dos fônons com o aumento da tensão de porta e esse efeito é o oposto do que é observado para os fônons com q=0. Nós mostramos que esse tipo de renormalização é uma assinatura dos fônons com vetor de onda q2K que vem de um processo de camada única, os modos de fônons que contribuem para a banda Raman G*, em ~2450cm-1 e para outros cinco picos provenientes de combinação de modos na região de frequência 1700-2300cm-1. Combinando a teoria do processo DRR com o efeito de renormalização de fônons, nós mostramos uma nova técnica para usar a Espectroscopia Raman para identificar cada modo Raman apropriadamente. Nó também estudamos o comportamento dos modos ópticos do grafeno de camada dupla combinando o espalhamento Raman e a aplicação de tensão de porta em dispositivos desse material. Nós observamos que a banda G se divide em duas quando o nível de Fermi da amostra é mudado e isso é explicado em termos da mistura dos modos de fônon Raman (Eg) e infravermelho (Eu) devido a diferença de concentração de carga nas duas camadas. Nós mostramos que a comparação entre os dados experimentais e o modelo teórico não dá apenas informação sobre a concentração de carga total no dispositivo de grafeno de camada dupla, mas também nos permite quantificar separadamente a quantidade de cargas não intencionais provenientes da camada de cima e de baixo do sistema e, portanto caracterizar a interação do grafeno de camada dupla com o ambiente a sua volta. Na segunda parte dessa tese, a dispersão de elétrons e fônons perto do ponto K do grafeno de camada dupla é investigada atravé do estudo da banda G' usando várias energias de excitação de laser na região do infravermelho e do visível. A estrutura eletrônica foi analisada dentro da aproximação de ligações-forte e os parâmetros Slonczewski-Weiss-McClure (SWM) foram obtidos através do comportamento dispersivo da banda G' considerando-se tanto o processo DRR interno, quanto o externo. Nós mostramos que os parâmetros SWM obtidos considerando-se que o processo DRR interno está em melhor acordo com os valores obtidos por outras técnicas experimentais, sugerindo fortemente que o processo interno é o principal responsável pela banda G' no grafeno. Além disso, a dependência da intensidade dos quatro picos que compõe a banda G' do grafeno de camada dupla com a energia de excitação de laser e com a potência do laser é explorada e explicada em termos do acoplamento elétron-fônon e do relaxamento dos elétrons foto-excitados. Nós mostramos que o relaxamento dos elétrons ocorre predominantemente pela emissão de fônons acústicos de baixa energia e as diferentes combinações dos processos de relaxamento determinam as intensidades relativas dos quatro picos que dão origem à banda G'. Esse efeito nos fornece informações importantes sobre a dinâmica dos elétrons e fônons e precisa ser levado em conta para aplicações do grafeno de camada dupla do campo nanotecnológico.
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Su, Tong. "MEASUREMENT OF F2n /F2p FROM DEEP INELASTIC ELECTRON SCATTERING OFF A = 3 MIRROR NUCLEI AT JEFFERSON LAB." Kent State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=kent1587680491082341.
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Sugimoto, Koudai. "Theoretical Study of Electron Dynamics in Multi-Orbital Antiferromagnetic Metals." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199089.
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Williams, Jennifer C. "Colour-singlet exchange and tests of models of diffractive DIS." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342246.
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Walsh, James Paul Slater. "Anisotropy in molecular magnetism." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/anisotropy-in-molecular-magnetism(11474b91-0d3d-4b0a-97cd-214d1713674e).html.
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A collection of studies are reported that focus on the examination of exchange interactions in complexes containing paramagnetic ions with a large magnetic anisotropy. A number of complementary techniques are used to analyse the complicated systems that arise, including high-field high-frequency electron paramagnetic resonance, inelastic neutron scattering, SQUID magnetometry, and ab initio calculations. The nuclearity of the complexes ranges from dimetallic, to trimetallic, to octametallic. A family of five water- and carboxylate-bridged nickel(II) dimetallics are the focus of a magneto-structural correlation study that succeeds in measuring the magnitude of the exchange interaction despite dominating effects from large zero-field splitting effects. Similar work is reported for four cobalt(II) analogues of these compounds, with the relationship between exchange interactions and geometry also being probed by pressure INS. Charge density studies that combine high resolution X-ray and neutron diffraction studies are reported on cobalt and nickel analogues from the same family of dimetallics, revealing strong evidence for non-direct exchange. A family of four trimetallic triangle complexes containing two nickel(II) ions and one chromium(III) ion bridged by a central fluoride and a total of six carboxylates are reported, and the exchange interactions are elucidated from a global model that accounts for the low-field magnetic, heat capacity, and EPR data. Two new octametallic vanadium(III) wheels—where each pair of adjacent metals are bridged by a fluoride and two carboxylates—are reported along with preliminary results from magnetic measurements and solid state proton NMR spectra, which reveal significant field-dependent effects arising from level crossings at high fields.
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Kundu, Ashoke. "Monte Carlo simulation of gas-filled radiation detectors." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/987/.
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Söderström, Johan. "Soft X-ray Scattering Dynamics Close to Core Ionization Thresholds in Atoms and Molecules." Doctoral thesis, Uppsala University, Department of Physics, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7832.
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In this Thesis studies of highly excited states in gas-phase atoms and molecules (He, Ne, N2, O2, N2O and CO2) using a variety of synchrotron-radiation based techniques are presented. The three techniques used most frequently are X-ray-emission-threshold-electron coincidence (XETECO), X-ray emission spectroscopy (XES) and X-ray photoelectron spectroscopy (XPS) and they are all given a brief introduction.
The fluorescence yield (FY) from doubly excited states in helium near the N=2 threshold(s) has been investigated in weak static external magnetic and electric fields, but also in a field free environment. The FY spectra in weak static magnetic fields show the importance of including the diamagnetic interaction in the theoretical models. The presence of weak static electric fields shows that even weak fields (as low as 44 V/cm) has a great impact on the observed FY spectra. Resonant XES spectra from some of the first doubly excited states in helium has been recorded in a field free environment, and compared to theory.
The XETECO technique is presented and the first XETECO results from Ne, N2, O2, CO2 and N2O are shown, together with interpretations of possible threshold dynamics. I show that XETECO can be interpreted as threshold photoelectron spectra free from post collision interaction, and can hence be compared to above threshold XPS measurements. The observed below-threshold structures in the XETECO spectra are discussed and given a tentative explanation. The results from the analysis of the N2O XETECO spectrum lead to further investigations using XPS. Results showing the vibrational parameters and vibrationally resolved cross-sections and asymmetry parameters for N2O are presented together with theoretical predictions.
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Luo, Chengtao. "Structural Study of Heterogeneous States in Lead-free NBT-based Single Crystals." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/73690.
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Growing environmental concerns, coupled with increasing regulatory restrictions, are requiring industries to develop non-lead-based compositions of ferroelectric and piezoelectric materials. These materials—now widely used in sensors, actuators, and transducers—are for the most part lead-based compounds such as Pb(Zr,Ti)O3 (PZT). Indeed, PZT represents the dominant market share for use in these technologies. Moreover, next generation compounds, which include Pb(Mg1/3Nb2/3)O3-xat%PbTiO3 (PMN-x%PT) crystals with ultrahigh piezo-/electromechanical properties, are also Pb-based systems and thus are problematic for meeting more restrictive environmental standards. As alternative, Pb-free ferroelectrics such as NBT-derived single crystals represent viable next-generation materials for use in ferro-/piezoelectric applications. Development of these types of NBT-based crystals has made important advancements in the last decade. In fact, the performances of NBT-based materials are beginning to approach the properties of the widely used commercial PZT ceramic material. Nonetheless, additional studies are needed before it being able to compete with PMN-x%PT and PZN-x%PT crystals in next-generation applications.
As a new type of piezoelectric material, much remains to be learned about Pb-free piezoelectric crystals. For instance, in addition to enhancing our understanding the nature of the piezoelectric third-rank tensor coefficients such as d33 and d15, a thorough knowledge of the Curie temperature, leakage current, and electromechanical properties is also essential for increasing the applications potential of these crystals. As detailed herein, multiple dopants may have to be incorporated into NBT to modify its microstructure and properties to meet these specific requirements, which may further complicate its chemical structure-property relationships.
This study, therefore, was designed to investigate the heterogeneous structure of NBT-based single crystals, using x-ray diffraction, transmission electron microscopy, and neutron inelastic scattering, with the goal of investigating the mechanism coupling of morphotropic phase boundary (MPB) and the maximum property responses in A-site disordered perovskite Pb-free piezoelectric systems. Using the framework of polar nanoregions and adaptive phase theory, I sought to determine how the nanostructure of these single crystals change with temperature and composition—and how these factors impact its properties. Diffuse scattering, domain morphology, and phonon dispersions were used to investigate both the static and dynamic properties of these heterogeneous structures.Ph. D.
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Zhang, Yao. "Experimental Measurements by Antilocalization of the Interactions between Two-Dimensional Electron Systems and Magnetic Surface Species." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/49020.
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Low-temperature weak-localization (WL) and antilocalization (AL) magnetotransport measurements are sensitive to electron interference, and thus can be used as a probe of quantum states. The spin-dependent interactions between controllable surface magnetism and itinerant electrons in a non-magnetic host provide insight for spin-based technologies, magnetic data storage and quantum information processing. This dissertation studies two different host systems, an In$_{0.53}$Ga$_{0.47}$As quantum well at a distance from the surface of a heterostructure, and an accumulation layer on an InAs surface. Both the systems are two-dimensional electron systems (2DESs), and possess prominent Rashba spin-orbit interaction caused by structural inversion asymmetry, which meets the prerequisites for AL. The surface local moments influence the surrounding electrons in two ways, increasing their spin-orbit scattering, and inducing magnetic spin-flip scattering, which carries information about magnetic interactions. The two effects modify the AL signals in opposing directions: the spin-flip scattering of electrons shrinks the signal, and requires a close proximity to the species, whereas the increase of spin-orbit scattering broadens and increases the signal. Accordingly, we only observe an increase in spin-orbit scattering in the study of the interactions between ferromagnetic Co$_{0.6}$Fe$_{0.4}$ nanopillars and the relatively distant InGaAs quantum well. With these CoFe nanopillars, a decrease in spin decoherence time is observed, attributed to the spatially varying magnetic field from the local moments. A good agreement between the data and a theoretical calculation suggests that the CoFe nanopillars also generate an appreciable average magnetic field normal to the surface, of value $\sim$ 35 G. We also performed a series of comparative AL measurements to experimentally investigate the interactions and spin-exchange between InAs surface accumulation electrons and local magnetic moments of rare earth ions Sm$^{3+}$, Gd$^{3+}$, Ho$^{3+}$, of transition metal ions Ni$^{2+}$, Co$^{2+}$, and Fe$^{3+}$, and of Ni$^{2+}$-, Co$^{2+}$-, and Fe$^{3+}$-phthalocyanines deposited on the surface. The deposited species generate magnetic scattering with magnitude dependent on their electron configurations and effective moments. Particularly for Fe$^{3+}$, the significant spin-flip scattering due to the outermost 3d shell and the fairly high magnetic moments modifies the AL signal into a WL signal. Experiments indicate a temperature-independent magnetic spin-flip scattering for most of the species except for Ho$^{3+}$ and Co$^{2+}$. Ho$^{3+}$ yields electron spin-flip rates proportional to the square root of temperature, resulting from transitions between closely spaced energy levels of spin-orbit multiplets. In the case of Co$^{2+}$, either a spin crossover or a spin-glass system forms, and hence spin-flip rates transit between two saturation regions as temperature varies. Concerning the spin-orbit scattering rate, we observe an increase for all the species, and the increase is correlated with the effective electric fields produced by the species. In both 2DESs, the inelastic time is inversely proportional to temperature, consistent with phase decoherence via the Nyquist mechanism. Our method provides a controlled way to probe the quantum spin interactions of 2DESs, either in a quantum well, or on the surface of InAs.Ph. D.
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Schuster, Roman. "Electron Energy-Loss Spectroscopy on Underdoped Cuprates and Transition-Metal Dichalcogenides." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-27333.
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Die vorliegende Arbeit befasst sich mit Elektronenenergieverlustspektroskopie an unterdotierten Kupratsupraleitern und Übergangsmetalldichalcogeniden. Nach einem kurzen Abriss über die der experimentellen Methode zugrundeliegenden theoretischen Tatsachen folgen zwei experimentelle Kapitel. Für das prototypische Kupratsystem Ca2-xNaxCuO2Cl2 wird für verschiedene Dotierungskonzentrationen zunächst die Entwicklung der Ladungstransferanregungen untersucht. Man findet eine substanzielle Umverteilung des spektralen Gewichtes, verbunden mit einem starken Einbruch der Dispersion dieser Anregungen. Beides wird im Rahmen der Wechselwirkung mit Spinfreiheitsgraden innerhalb der Kupfer-Sauerstoff-Ebene diskutiert. Anschliessend erfolgt die Diskussion einer ausschließlich für zehnprozentige Dotierung auftretenden Symmetriebrechung der optischen Antwortfunktion, für die verschiedene mögliche Szenarien vorgeschlagen werden. Im Kapitel über die Dichalcogenide liegt der Fokus auf dem Verhalten des Ladungsträgerplasmons, das für alle Substanzen dieser Gruppe mit Ladungsordnung eine negative Dispersion aufweist. Dieses Verhalten läßt sich durch in-situ Interkalation zusätzlicher Ladungstraeger umkehren, so dass man eine dotierungsabhängige Plasmonendispersion erhält. Es werden verschiedene Szenarien für dieses Verhalten diskutiertThe present thesis describes electron energy-loss spectroscopy on underdoped cuprate superconductors and transition-metal dichalcogenides. After a brief introduction into the experimental method there are two experimental chapters. For the prototype cuprate system Ca2-xNaxCuO2Cl2 the behavior of the charge-transfer excitations is investigated as a function of doping. The observed substantial redistribution of spectral weight and the accompanying breakdown of their dispersion is discussed in terms of a coupling to the spin degrees of freedom within the copper-oxygen plane. For x=0.1 there is a pronounced symmetry breaking in the optical response function which is discussed in terms of different possible scenarios. The chapter on the dichalcogenides focuses on the properties of the charge-carrier plasmon which shows a negative dispersion for all representatives of this family exhibiting a charge-density wave instability. This behavior can be influenced by in-situ intercalation of additional charges, the result being a doping dependent plasmon dispersion. Several approaches to reconcile these findings are considered
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White, Glen R. "Tests of perturbative and non-perturbative QCD from identified proton, kaon and pion studies in deep inelastic scattering ep interactions at HERA." Thesis, Lancaster University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369500.
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Záchej, Samuel. "Monte Carlo simulace elektronového rozptylu v rastrovacím prozařovacím elektronovém mikroskopu." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-242036.
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This thesis deals with an electron scattering in STEM microscopy on objects with dif-ferent shapes, such as cuboid, sphere and hollow capsule. Monte Carlo simulations are used for description of multiple electron scattering. Except the theoretical analysis of the electron scattering and simulation methods, the thesis contains design and realiza-tion of an algorithm simulating electron scattering in given objects. In addition, there is a design for robustness evaluation of the simulation, based on comparison between results and known signals for a given object. Reliability of the algorithm was verified by experimental measurements of the electron scattering on a carbon layer.
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Greenwood, Jason B. "Elastic and inelastic scattering of electrons from ions." Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282155.
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Röder, Falk. "Off-Axis Elektronenholographie elastisch und unelastisch gestreuter Elektronen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-115245.
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Die Off-Axis-Elektronenholographie ist eine interferometrische Methode zur experimentellen Bestimmung von relativen Phasenschiebungen einer Elektronenwelle. Der Zugang zu diesen Phasenschiebungen ermöglicht z.B. die Bestimmung von intrinsischen elektrischen und magnetischen Feldern eines Objektes im Nanometerbereich. Für eine quantitative Interpretation der Resultate ist die Kenntnis des Rauschens der holographisch rekonstruierten Größen von hoher Bedeutung. In dieser Arbeit wird ein allgemeiner Formalismus abgeleitet, der den Rauschtransfer vom detektierten Hologramm in die rekonstruierten Amplituden- und Phasenbilder beschreibt. Anhand zielgerichteter Experimente wird dieser Formalismus unter Berücksichtigung von gemessenen Rauscheigenschaften des Detektors verifiziert. Im Zuge dessen wird eine experimentelle Methode entwickelt, die es erlaubt, durch Serienaufnahmen und Mittelungsprozeduren das Signal-zu-Rauschverhältnis in den holographischen Resultaten bei gleichbleibender Ortsauflösung erheblich zu verbessern. Daran knüpft sich eine Vielzahl von Anwendungen an, welche in dieser Arbeit in Auszügen aufgeführt werden. Die Grundlage für all diese Experimente besteht in den Welleneigenschaften des Elektrons, welche in der Interferenzfähigkeit (Kohärenz) des Elektrons zum Ausdruck kommen. Elektronen, welche unelastisch an einem Objekt streuen, verlieren diese Eigenschaft und es stellt sich die Frage, ob aus diesem Verlust zusätzliche Informationen über den Streuprozess bzw. über das Objekt selbst gewonnen werden können. Eine Größe, die neben der Intensität auch die Kohärenz der Elektronen beschreibt, ist die reduzierte Dichtematrix. Das motiviert, die Methode der Off-Axis-Elektronenholographie in der Sprache der Dichtematrizen zu formulieren und eine allgemeine Übertragungstheorie für ein holographiefähiges Transmissionselektronenmikroskop abzuleiten. Diese Theorie umfasst alle bisher bekannten Phänomene im Rahmen der Elektronenholographie und bietet darüber hinaus neue instrumentelle Ansätze zur Optimierung des Signal-zu-Rausch-Verhältnisses und zur Überwindung auflösungsbegrenzender Aberrationen. Vor diesem Hintergrund wird weiterhin die Kohärenz von Elektronen mittels energiegefilterter Off-Axis-Elektronenholographie untersucht, welche unelastisch an Siliziumoberflächen streuen und charakteristische Oberflächenplasmonen anregen. Für die Interpretation der Resultate werden zwei Modelle für die Dekohärenz des Elektrons infolge der Wechselwirkung mit einer Objektoberfläche entwickelt und unter Berücksichtigung der Aberrationen des Energiefilters mit dem Experiment verglichenOff-axis electron holography provides access to the relative phase shift of an electron wave and allows the experimental determination of intrinsic electric and magnetic fields within an object at nanometre scale. A quantitative interpretation of the results requires the knowledge about the noise in the reconstructed data. In this work, a general formalism is derived describing the transfer of noise from an experimental hologram into reconstructed amplitude and phase images. Concerted experiments verify this formalism under consideration of measured noise properties of the detector. In this frame, a method based on series acquisition and averaging is developed to improve significantly the signal-to-noise ratio of the reconstructed amplitude and phase images at constant spatial resolution. The usefulnes of this method is demonstrated by selected experimental examples from the materials sciences. The capability to show interference, i.e. to be coherent, is a consequence of the electron's wave nature and provides the fundament for all applications of electron holography. By inelastic interaction with the object, the electron loses coherence and the question comes up, whether this loss mechanism contains additional information about the scattering process or even about the object itself. The reduced density matrix is introduced as a suitable quantity describing both intensity and coherence of scattered electrons. That motivates to formulate off-axis electron holography in the language of density matrices and to derive a general transfer theory for this quantity in a holography-dedicated transmission electron microscope. This theory reproduces all known phenomena related to off-axis electron holography and provides new instrumental approaches to improve the signal-to-noise ratio and to overcome resolution limiting aberrations. In this context, the coherence of electrons, which are inelastically scattered by silicon surfaces and have excited characteristic surface plasmons, is investigated by energy-filtered electron holography. For the interpretation of the experimental results, two models are developed for the decoherence of the electron by interaction with an object surface and are compared to the experiment under consideration of the aberrations of the energy-filter
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McCance, Gavin John. "Event shapes and power corrections at HERA." Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342040.
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Rossi, Matteo. "La diffusion inélastique résonante de rayons X sur systèmes corrélés induit par l'interaction spin-orbite : applications scientifiques et développements instrumentaux." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY089/document.
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Les oxydes d’iridium (iridates) ont attiré particulière attention au cours de la dernière décennie grâce à l’identification d’un état isolant de Mott induit par l’action conjointe du champ cristallin, de la corrélation électronique et du couplage spin-orbite. Cet état a été intensément investigué et des phases et excitations nouvelles ont été prédites théoriquement et aussi individuées expérimentalement. Sans doute, la diffusion inélastique résonante de rayons X (RIXS) est l’une des techniques les plus adoptée pour mesurer les excitations à basse énergie des iridates. En effet, la section efficace relativement large de la spectroscopie RIXS au seuil L3 de l’iridium et la bonne résolution en énergie ont encouragé l’emploi de cette technique. Cette thèse se pose un double objectif : concevoir des développements instrumentaux ayant pour but d’améliorer les possibilités offertes par la spectroscopie RIXS, et appliquer le RIXS afin d’étudier la physique à basse énergie de certains iridates.Le principal projet de développement instrumental est un nouveau spectromètre RIXS avec résolution en polarisation. L’analyse de la polarisation des rayons X diffusés permet d’obtenir des informations sur la symétrie et donc la nature des excitations. Cependant, elle est peu employée à cause de problèmes techniques qui naissent quand l’on veut préserver aussi la résolution en énergie et l’efficience du spectromètre. Même si le polarimètre RIXS projeté n’est pas encore disponible, le schéma optique a été vérifié et validé. Le polarimètre aura une résolution en énergie et une efficience équivalentes à celles des spectromètres RIXS courants. Le second développement technique comprend l’équipement permettant de réaliser des mesures RIXS à basse température et haute pression. Ces équipements ont permis d’investiguer l’évolution en pression des excitations magnétique du composé Sr3Ir2O7 en dessous de la température de Néel et jusqu’au 12 GPa. Les mesures peuvent aider l’affinage des modèles magnétiques courants pour ce système. Ces mesures démontrent que les excitations magnétiques peuvent être acquises en haute pression par la spectroscopie RIXS, démontrant ainsi la possible utilisation de cette technique dans ce nouveau domaine.Cette thèse comprend aussi des ultérieurs travails expérimentaux. Le premier considère le composé CaIrO3, dont la structure cristalline est constituée par des octaèdres partageant un sommet et une arête dans deux directions orthogonales. Du coup, les interactions magnétiques sont très différentes selon la direction cristallographique. Spécifiquement, la suppression du couplage de type Heisenberg dans la direction où les octaèdres partagent une arête produit des interactions magnétiques principalement unidimensionnelles. La caractéristique de ceux-ci est la présence d’un continuum d’excitations avec une dépendance en énergie et quantité de mouvement typique, qui a été révélé par la spectroscopie RIXS. Les excitations électroniques de CaIrO3 ont aussi des caractéristiques propres. Enfin, j’ai étudié les propriétés électroniques du composé Rb2[IrF6]. Des calculs récents proposaient que ce système possède un état d’isolant de Mott similairement aux oxydes d’iridium. Les mesures RIXS ont aidé à éclairer les propriétés électroniques de ce composé. La solidité des propriétés électroniques a été vérifiée par rapport à la substitution du métal alcalin ou de l’halogène, et à l’application de pression.Cette thèse accroit l’importance de l’utilisation de la spectroscopie RIXS dans des domaines qui étaient précédemment inexplorés. L’analyse de la polarisation des rayons X diffusés sera avantageuse dans les cas où la nature des excitations ne peut être établie sans ambiguïté. L’équipement développé pour réaliser les mesures RIXS en conditions extrêmes permet d’étudier la dynamique électronique et magnétique dans des phases de la matière inaccessibles jusqu’à aujourd’huiIridium oxides (iridates) have raised notable attention in the last decade due to the identification of a Mott insulating state realized by the joint action of crystal field, electron correlation, and spin-orbit coupling. Such state has been intensively investigated and novel quantum phases and excitations have been theoretically predicted and experimentally found. Undoubtedly, one of the most employed techniques to elucidate the low-energy physics of iridates is resonant inelastic X-ray scattering (RIXS). At the iridium L3 edge, it benefits from a particularly good energy resolution, which matches the energy scales of the relevant excitations, and from a favorable inelastic cross-section. The aim of the present thesis is twofold: conceive challenging instrumental upgrades that contribute to the advancement of the technique itself, and apply RIXS to inspect the magnetic and electronic properties of selected iridates.The main instrumental development concerns the design of a new RIXS spectrometer with polarization resolution. Polarization analysis of the scattered X-rays provides useful information about the symmetry and thus the nature of an excitation. However, it is rather unexploited because of severe technical challenges when energy resolution and efficiency must be preserved. The designed RIXS spectrometer with polarization analysis capabilities is still under construction, however the optical scheme has been validated by preliminary tests. Full polarization analysis is expected without degradation of energy resolution or efficiency with respect to current state-of-the-art RIXS spectrometers. Additional technical developments include sample-environment equipment to perform RIXS experiments in low-temperature and high-pressure conditions. The equipment has been successfully utilized to investigate the magnetic dynamics of the bilayer-perovskite Sr3Ir2O7 below its Néel temperature and up to 12 GPa. Our measurements provide additional observations that may sharpen the challenge to theoretical understanding of the magnetic dynamics of this material. Moreover, we demonstrate for the first time that RIXS experiments of the magnetic dynamics can be extended to unexplored thermodynamic conditions.Besides instrumental advances, additional experimental work has been carried out in order to study the magnetic and electronic excitations of the post-perovskite CaIrO3. Owing to its peculiar crystal structure, featuring both edge- and corner-sharing octahedra, the magnetic interactions of CaIrO3 are very different along orthogonal directions. In particular, the inhibition of the Heisenberg coupling along the edge-sharing direction induces one-dimensional magnetic behavior with characteristic fractional spinon-like excitations, which have been detected by RIXS. Electronic excitations are also found to have particular properties. Finally, I have focused on the electronic structure of Rb2[IrF6], which was theoretically predicted to realize a Mott insulating state similar to the one of iridium oxides. RIXS measurements helped to elucidate the electronic properties of this compound. The robustness of the electronic state has been tested against substitutions of the alkali metal and halogen, and application of physical pressure.The present work extends the potential of the RIXS technique to domains previously unexplored, i.e. polarization analysis of the scattered X-rays and high-pressure low-temperature experiments. I hope that the instrumental upgrades and applications of RIXS discussed in this thesis will further promote the technique as a powerful and reliable tool to characterize elementary excitations in correlated-electron systems
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Hasch, Delia. "Messung der polarisierten Strukturfunktion g1(x, Q 2) des Protons mit dem HERMES-Experiment." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 1999. http://dx.doi.org/10.18452/14523.
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Die vorliegende Arbeit beschreibt die Messung der polarisierten Strukturfunktion g1p des Protons in der polarisationsabh"angigen tief inelastischen Positron-Proton-Streuung bei einer Schwerpunktenergie von 7.5 GeV. Die Analyse umfasst die 1997 mit dem Hermes-Experiment am Hera-Positronring aufgezeichneten Daten der Streuung polarisierter Positronen der Energie 27.6 GeV an einem polarisierten Wasserstofftarget. Aus den Z"ahlraten der inklusiv nachgewiesenen, selektierten Positronen f"ur die parallele und die antiparallele Ausrichtung der Spinvektoren von Strahlteilchen und Targetatomen wurde die Streuquerschnitts- Asymmetrie der Positron-Proton-Streuung bestimmt. In verschiedenen Korrekturverfahren wurden Untergrundprozesse, Spektrometereinfl"usse sowie Strahlungskorrekturen ber"ucksichtigt. Die Untergrundkorrekturen wurden aus den Daten, die Spektrometerkorrekturen aus einer Monte-Carlo- Simulation ermittelt. Die Abh"angigkeit der Monte-Carlo- und Strahlungskorrekturen von der gew"ahlten Modell-Asymmetrie zur Beschreibung der polarisationsabh"angigen Effekte wurde durch die Anwendung eines iterativen Verfahrens minimiert. Aus der vollst"andig korrigierten Streuquerschnitts-Asymmetrie wurde die Asymmetrie g1/F1 im kinematischen Bereich 0.021 < x < 0.85 und Q2 > 0.8 GeV^2 mit einer systematischen Unsicherheit von etwa 8% bei einer statistischen Genauigkeit von 6% bis 20%, ansteigend f"ur abnehmende x-Werte, bestimmt. Die aus g1/F1 berechnete polarisierte Strukturfunktion g1p(x,Q2) wird, unter der Annahme einer von q2 unabh"angigen Asymmetry g1/F1, zu einem festen Wert Q2_0 entwickelt. Ihr erstes Moment im gemessenen x-Bereich betr"agt int_{0.021}^{0.85} dx g1p(x,Q2_0) = 0.122 =- 0.003 (stat) =- 0.010 (sys) at Q2_0 = 2.5 GeV^2. Der Vergleich mit den Werten des SMC-Experimentes am CERN und des E143-Experimentes am SLAC f"ur das erste Moment von g1p wurde unter Anwendung des gleichen Integrationsschemas f"ur den jeweils gemeinsam gemessenen x-Bereich sowie f"ur gleiche Q2_0 Werte durchgef"uhrt. Das Ergebnis der vorliegenden Analyse befindet sich, bezogen auf die statistische Genauigkeit der Messungen, in "Ubereinstimmung innerhalb von 0.6 bzw. 1.2 Standardabweichungen mit den Resultaten des E143- bzw. SMC-Experimentes. Durch Extrapolation der Strukturfunktion auf den gesamten x-Bereich [0,1] wird das erste Moment zu \int_{0}^{1} dx g1p(x,Q2_0) = 0.132 +- 0.003 (stat) +- 0.010 (sys) +- 0.006 (extr) bestimmt, wobei der zus"atzliche Fehler die Unsicherheit in der Extrapolation x -> 0 wiedergibt. Die Interpretation der vorliegenden Messung im Rahmen des Quark-Parton-Modells unter Ber"ucksichtigung von QCD-Korrekturen der Ordnung O(alphaS^3) ergibt einen Beitrag der Quarks zum Gesamtspin des Nukleons von (30 +- 10)% f"ur Q2_0 = 2.5 GeV^2. Dieses Ergebnis entspricht einer Abweichung von der Ellis-Jaffe-Vorhersage um 2.5 Standardabweichungen, bezogen auf den angegebenen Gesamtfehler, und f"uhrt im Kontext des Quark-Parton-Modells zur Interpretation negativ polarisierter Strange-Seequarks mit einem Beitrag von (-9 +- 4)% f"ur Q2_0 = 2.5 GeV^2. Von verschiedenen Gruppen werden aus QCD-Analysen unterschiedlicher Datens"atze Beitr"age der Quarks zum Nukleonspin von 19% bis 44% angegeben. Unter Hinzunahme der Hermes-Messung der polarisierten Neutronstrukturfunktion g1n wurde der Wert der fundamentalen Bjorken-Summenregel f"ur Q2_0 = 2.5 GeV^2 bestimmt. Dieser Wert befindet sich, bei einer auf den Gesamtfehler bezogenen Genauigkeit von 13%, innerhalb von 0.5 Standardabweichungen in "Ubereinstimmung mit der theoretischen Vorhersage, berechnet unter Ber"ucksichtigung von QCD-Korrekturen der Ordnung O(\alphaS^3).The subject of this thesis is the measurement of the polarised structure function g1p of the proton in deeply inelastic positron-proton-scattering at a centre of mass energy of 7.5 GeV. The data used in the analysis were recorded during the 1997 running period of the Hermes experiment using a longitudinally nuclear polarised hydrogen target in the 27.6 GeV Hera polarised positron storage ring. The cross section asymmetry of positron-proton-scattering has been measured by counting the number of inclusively reconstructed and selected positrons with target spin vector parallel or antiparallel to the beam spin direction. Background processes, spectrometer effects, and radiative corrections have been taken into account by applying different correction procedures. Here background corrections were determined from data while spectrometer corrections were computed from Monte Carlo simulation. The dependence of Monte Carlo and radiative corrections on the model asymmetry chosen to describe polarisation dependent effects has been minimised by applying an iterative procedure. From the fully corrected cross section asymmetry the asymmetry g1/F1 has been computed in the kinematic region 0.021 < x < 0.85 and Q2 > 0.8 GeV^2 with a systematic uncertainty of 8% and a statistical accuracy of 6% to 20%, raising for decreasing x values. The polarised structure function g1p(x,Q2), determined from the asymmetry g1/F1 , was evoluted to a common Q2_0 value assuming g1/F1 to be independent of Q2. Its first moment evaluated in the measured x region is int_{0.021}^{0.85} dx g1p(x,Q2_0) = 0.122 =- 0.003 (stat) =- 0.010 (sys) at Q2_0 = 2.5 GeV^2. This result has been compared with those from E143 at SLAC and from SMC at CERN, both calculated with the same integration scheme and for the kinematic range of Hermes. With respect to the statistical uncertainties the agreement is better than 0.6 and 1.2 standard deviations, respectively. Extrapolation over the entire x range [0,1] yield for the first moment\int_{0}^{1} dx g1p(x,Q2_0) = 0.132 +- 0.003 (stat) +- 0.010 (sys) +- 0.006 (extr) where the additional error gives the uncertainty in the extrapolation x -> 0. The interpretation of this measurement in the framework of the quark parton model taking QCD corrections of the order O(alphaS^3) into account results in a contribution of the quarks to the total nucleon spin of (30 +- 10)% at Q2_0 = 2.5 GeV^2. This result corresponds to a deviation from the Ellis-Jaffe prediction by 2.5 standard deviation regarding the given total uncertainty. Within the quark parton model the deviation can be interpreted as negative polarisation of the strange sea quarks with a contribution of (-9 +- 4)% at Q2_0 = 2.5 GeV^2. Different groups give contributions of the quarks to the nucleon spin of 19% to 44% which were obtained from QCD analyses of various data sets. The fundamental Bjorken sum rule has been determined at Q2_0 = 2.5 GeV^2 using the Hermes measurement of the polarised neutron structure function g1n. With respect to the experimental accuracy of 13 %, the result agrees within 0.5 standard deviation with the theoretical prediction taking QCD corrections of the order O(alphaS^3) into account.
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Hagiya, Toru. "Electronic Excitation and Density Response in Liquid Alkali Metals Studied by Inelastic X-ray Scattering." Kyoto University, 2020. http://hdl.handle.net/2433/253075.
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Shehzadi, Ramoona [Verfasser]. "Measurement of beauty production in deep inelastic scattering at HERA using decays into electrons / Ramoona Shehzadi. Mathematisch-Naturwissenschaftliche Fakultät." Bonn : Universitäts- und Landesbibliothek Bonn, 2011. http://d-nb.info/1016263147/34.
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CAMPOS, MARIA C. A. "Espalhamento inelastico de eletrons no sup(12) C." reponame:Repositório Institucional do IPEN, 2001. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10947.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Weber, Frank. "Probing electronic phase transitions with phonons via inelastic neutron scattering : superconductivity in borocarbides, charge and magnetic order in manganites$nElektronische Ressource /." [S.l. : s.n.], 2007. http://digbib.ubka.uni-karlsruhe.de/volltexte/1000007516.
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Rakoto, Harison. "Localisation electronique dans les amorphes metalliques : etude sous champ magnetique intense." Toulouse 3, 1986. http://www.theses.fr/1986TOU30036.
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Mesures de resistivite et de magnetoresistance sur divers alliages metalliques amorphes. Les resultats sont interpretes en termes de localisation faible, d'interactions interelectroniques et eventuellement de fluctuations supraconductrices. Dans le cas d'alliages supraconducteurs (lanthane-aluminium, lanthane-gallium, cuivre-zirconium), on discute les limites de validite des modeles theoriques actuels. Mise en evidence des effets de localisation sur la supraconductivite (vanadium-silicium) par des mesures de variation du champ critique avec la temperature. Pour ce qui est des alliages non supraconducteurs, l'analyse des resultats en champ magnetique fort permet une determination relativement precise des temps de relaxation inelastique et spin-orbite
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Wang, Tao. "Excitation électrique de plasmons de surface avec un microscope à effet tunnel." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00868784.
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Pour la première fois, en associant un microscope à effet tunnel (STM) et un microscope optique inversé,nous avons imagé les plasmons de surface excités électriquement sur un film d'or avec la pointe d'un STM.Par microscopie de fuite radiative, en observant l'image de l'interface air/or et celle du plan de Fourierassocié, nous avons distingué les plasmons propagatifs des plasmons localisés sous la pointe. Les plasmonspropagatifs sont caractérisés par une distance de propagation et une direction d'émission en accord aveccelles de plasmons propagatifs créés par excitation laser sur des films d'or de mêmes épaisseurs. Les fuitesradiatives des plasmons localisés s'étalent jusqu'à l'angle maximum d'observation. Plasmons propagatifs etlocalisés ont une large bande spectrale dans le visible. Si la pointe est plasmonique (en argent), lesplasmons localisés ont une composante supplémentaire due au couplage associé. Pour différents types depointe, nous avons déterminé les intensités relatives des plasmons localisés et propagatifs. Nous trouvonsque chaque mode plasmon (propagatif ou localisé) peut être préférentiellement sélectionné en modifiant lematériau de la pointe et sa forme. Une pointe en argent produit une intensité élevée de plasmons localisés,tandis qu'une pointe fine de tungstène (rayon de l'apex inférieur à 100 nm) produit essentiellement desplasmons propagatifs. Nous avons étudié la cohérence spatiale des plasmons propagatifs excités par la pointe du STM. Avec un film d'or opaque (épaisseur 200 nm) percé de paires de nanotrous nous avons réalisé une expérienceanalogue à celle des fentes d'Young. Des franges d'interférences sont observées. La mesure de leurvisibilité en fonction de la distance des nanotrous donne une longueur de cohérence des plasmons de 4.7±0.5 μm. Cette valeur, très proche de la valeur 3.7± 1.2 μm déduite de la largeur de la distribution spectraledes plasmons, indique que l'élargissement spectral des plasmons propagatifs est homogène.Nous avons aussi étudié la diffusion des plasmons propagatifs excités par la pointe du STM par desnanoparticules d'or déposées sur un film d'épaisseur 50 nm. Nous observons une diffusion élastique et unediffusion radiative. Des franges d'interférences sont observées dans la région d'émission lumineuseinterdite du plan de Fourier, dont la période est inversement proportionnelle à la distancepointe-nanoparticule d'or avec un facteur de proportionnalité égal à la longueur d'onde moyenne desplasmons. Il y a donc interférence entre la radiation des plasmons localisés et la radiation provenant de ladiffusion des plasmons propagatifs sur les nanoparticules d'or. Ceci indique que les plasmons localisés etpropagatifs excités électriquement par la pointe du STM sont différentes composantes du plasmon uniqueproduit par effet tunnel inélastique avec la pointe du STM. Ces résultats originaux sur les plasmons créés sur film d'or par un effet tunnel inélastique localisé à l'échelle atomique (i) élargissent la compréhension du processus et (ii) offrent des perspectives intéressantes pour une association de la nanoélectronique et de la nanophotonique.
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Raymond, Stéphane. "Excitations de basse énergie dans les fermions lourds par diffusion inélastique des neutrons." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10103.
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La technique de diffusion inelastique des neutrons a ete utilisee pour caracteriser le spectre des excitations magnetiques de basse energie dans les composes a electrons fortement correles cenisn, ce#1#-#xla#xru#2si#2 et ceru#2ge#2. Cenisn est un compose kondo semimetallique dont le spectre des excitations magnetiques est compose de deux modes d'energie 2 et 4 mev et respectivement piques au centre et bord de zone de brillouin. L'application d'un champ magnetique met en evidence la nature differente de ces modes : le premier se deplace vers les plus hautes energies et la reponse du second s'elargit. Les modeles de gap d'hybridation particularises pour ce compose permettent de relier le mode a 4 mev aux proprietes macroscopiques observees. La dynamique des moments magnetiques pres d'une instabilite magnetique a ete etudiee dans le compose ce#1##xla#xru#2si#2 avec x = 0. 075. De facon surprenante, un ordre magnetique non conventionnel a ete mis en evidence (m = 0. 02 #b et t#n = 1. 8 k). La dynamique de spin par rapport au compose pur a ete reliee, grace a la theorie des fluctuations de spin de moriya, aux mesures macroscopiques. L'application d'un champ magnetique sur le compose ceru#2si#2 met en evidence le changement de la reponse dynamique du systeme de part et d'autre de la transition pseudometamagnetique. La reponse quasielastique et a courte portee a bas champ est remplacee par un ordre statique a longue distance en champ fort (h = 12 t). Dans ce contexte, la phase antiferromagnetique du compose ferromagnetique ceru#2ge#2 a ete caracterisee. Il existe alors une analogie entre ce compose sous sa temperature de curie et ceru#2si#2 au dessus du champ metamagnetique.
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Gedik, Nuh. "Recombination and propagation of quasiparticles in cuprate superconductors." Berkeley, Calif. : Oak Ridge, Tenn. : Lawrence Berkeley National Laboratory ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/842568-Q1sG4c/native/.
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doctoral thesis, Ph.D, University of California, Berkeley, Berkeley, CA.Published through the Information Bridge: DOE Scientific and Technical Information. "LBNL--55855" Gedik, Nuh. USDOE Director. Office of Science. Office of Basic Energy Sciences 05/20/2004. Report is also available in paper and microfiche from NTIS.
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Penha, Felipe Campos. "Efeitos de canais inelásticos no transporte eletrônico: um exemplo além do formalismo de Landauer." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-19032013-082632/.
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Neste trabalho, estudamos a influência de canais de espalhamento inelástico no transporte eletrônico. Primeiramente, expomos o formalismo de Landauer usual para o cálculo da corrente elétrica em sistemas em que o espalhamento é puramente elástico. Como exemplo, calculamos a corrente para um potencial delta de Dirac a partir de suas probabilidades de transmissão. A amostra correspondente é aquela de uma camada muito fina com impurezas (não-magnéticas) contida em uma heterostrutura semicondutora. Mostramos que a distorção do potencial quântico devido à voltagem aplicada pode ser desprezada no cálculo da corrente elétrica, abaixo da energia de Fermi do emissor. Subsequentemente, acoplamos o potencial delta a um oscilador harmônico quântico para modelar a presença de fônons no sistema. Encontramos modos inelásticos de transmissão que se tornam acessíveis para energias cada vez maiores, múltiplas do quantum hω. Devido à conservação de probabilidade, a abertura de cada novo canal corresponde a bicos\" nas probabilidades de transmissão dos modos abaixo deste, em função da energia de incidência do elétron. No caso de uma delta atrativa, ressonâncias assimétricas com perfil de Fano são observadas. Adaptamos o formalismo de Landauer, incluindo canais inelásticos independentes. Seguindo um trabalho anterior de Emberly e Kirczenow (2000), mostramos que existe uma forma de se levar em conta possíveis coincidências nos estados de espalhamento finais aplicando o princípio de exclusão de Pauli. Isto leva as distribuições dos estados de espalhamento a estarem fora de equilíbrio, já que dependem umas das outras. Resolvendo o problema auto-consistentemente, somos capazes de obter a corrente elétrica a partir das probabilidades de transmissão do potencial quântico. Nossos resultados demonstram que as ressonâncias de Fano do potencial atrativo dão origem a uma diminuição da inclinação da corrente elétrica contra a voltagem aplicada, já que elétrons são presos\" ao potencial por um tempo infinito. Mostramos este efeito num regime de voltagens baixas em comparação com a energia de Fermi, para o qual desprezamos a distorção do potencial quântico devido à voltagem aplicada. Além disso, uma comparação com os resultados do formalismo de Landauer mostra que uma discrepância significativa é observada para o caso de o oscilador estar inicialmente excitado e fortemente acoplado ao elétron.In this work, we study the influence of inelastic scattering channels in electronic transport. We first present the usual Landauer formalism, for calculating the electric current in systems where the scattering is purely elastic. As an example, we calculate the current for a Dirac delta potential from its transmission probabilities. The corresponding sample is that of a very thin layer with (non-magnetic) impurities within a semiconductor heterostructure. We show that the distortion of the quantum potential due to the applied voltage can be ignored in the calculation of an electric current below the Fermi energy of the emitter. Then we couple the delta potential to a quantum harmonic oscillator to model the presence of phonons in the system. We find inelastic transmission modes that become available for increasing energies, multiple of the quantum hω. Due to conservation of probability, the opening of each new channel corresponds to kinks\" in the transmission probabilities of lower modes as a function of the energy of the impinging electrons. In the case of an attractive delta potential, asymmetric resonances with a Fano-like profile are observed. We adapt the Landauer formalism by including the independent inelastic channels. Following a previous work by Emberly and Kirczenow (2000), we show that there is a way to take into account the possible coincidences in the final scattering states using Pauli\'s exclusion principle. This causes the distributions of the scattering states to be out of equilibrium, as they depend on each other. Solving the problem self-consistently, we are able to obtain the electric current from the transmission probabilities of the quantum potential. Our results demonstrate that the Fano resonances of the attractive potential gives rise to a decrease of the slope in the electric current versus the applied voltage, as the electrons are trapped\" in the potential for a finite amount of time. We have shown this effect in a low voltage regime with respect to the Fermi energy, for which we ignore the distortion of the quantum potential due to the applied voltage. Furthermore, a comparison with the results from the Landauer formalism shows that a significant discrepancy is seen for the oscillator initially in its excited mode and strongly coupled to the electron.
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Grenier, Philippe. "Etude des fonctions de structure en spin du nucleon : l'experience e143 au slac." Clermont-Ferrand 2, 1995. http://www.theses.fr/1995CLF21720.
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Cette these decrit l'experience e143 de diffusion profondement inelastique d'electrons de 29 gev sur des cibles de nh#3 et nd#3 polarisees. Elle s'est deroulee aupres de l'accelerateur de stanford, en californie, et son but etait de mesurer les fonctions de structure polarisees g#1 et g#2 sur le proton et le deuton. Ces fonctions de structure permettent de tester la regle de somme de bjrken, regle fondamentale de la chromodynamique quantique. Elles nous renseignent egalement sur la structure en spin du nucleon et, en particulier, elles permettent d'acceder a la fraction du spin du nucleon portee par les quarks. Experimentalement, on determine les fonctions de structure par la mesure d'asymetries en sections efficaces. Nous obtenons pour le premier moment de g#1, pour le proton et le deuton, des valeurs qui se situent de deux a trois deviations standards en dessous des predictions d'ellis et jaffe, mais nos resultats confirment la validite de la regle de somme de bjrken et permettent d'estimer a environ 30% la contribution des quarks au spin du nucleon. Nos resultats sur g#2 semblent etre bien decrits par l'expression de wandzura et wilczek
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Augustsson, Andreas. "Soft X-ray Emission Spectroscopy of Liquids and Lithium Battery Materials." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4526.
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Hérault, Joël. "Etude experimentale du ralentissement d'ions lourds de 20 a 100 mev par nucleon dans la matiere." Toulouse 3, 1988. http://www.theses.fr/1988TOU30075.
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Etude experimentale a l'aide d'ions lourds de l'accelerateur ganil sur le spectrometre lise (analyse en energie et en angle) pour determiner le pouvoir d'arret de 11 cibles gazeuses avec une incertitude de plus ou moins 3%. Mise en evidence d'une disparition de la difference entre pouvoirs d'arret des materiaux solides et gazeux lorsque la charge de l'ion tend vers son numero atomique. Analyse des distributions en energies pour de nombreux ions (de l'oxygene au molybdene) et analyse de la distribution angulaire dans des cibles solides et gazeuses. Comparaison des donnees experimentales aux calculs quantiques et classiques