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Dissertations / Theses on the topic 'Molecular collision theory'
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1
Hu, Xiao-ming. "Angle resolved photoelectron spectroscopy study of small molecules." Thesis, University of Aberdeen, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277242.
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Under the title 'Angle Resolved Photoelectron Spectroscopy Study of Small Molecules', the thesis discussed the following aspects: Processes after the interaction of photons with atoms or molecules, including photoscattering, photoexcitation and fluorescence, photoabsorption, photodissociation and photoionization; Concepts of photoionization and photoelectron spectroscopy, including ionization potentials, photoionization cross sections, photoelectron angular distributions, shape resonances and autoionization; Theory of photoionization and photoelectron angular distributions, including central field approximation, Hartree-Fock calculations and multichannnel quantum defect theory; Apparatus for an angle resolved high resolution photoelectron experiment, including the synchrotron radiation source at Daresbury Laboratory, UK and an angle resolved electron spectrometer system from NIST/ANL, USA; The experiment on CO2 at Daresbury Laboratory, including electron spectrometer calibrations, experimental procedures and data processing; Results and discussion, including results for the photoionization cross sections of the CO+2X2 Πh state, vibrational branching ratios and asymmetry parameters for the synmmetric stretch vibrations (000) to (500) in the CO+2X2 Πh state in the photon wavelength region of 687 - 790AA with a resolution of about 0.1AA, analysis of photoelectron spectra taken at the Tanaka-Ogawa resonances and result for the Franck-Condon factors for transitions from the autoionizing states to different vibrational levels of the molecule.
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Manolopoulos, David Eusthatios. "Close-coupled equations : the log derivative approach to inelastic scattering, bound state and photofragmentation problems." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254402.
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Randeniya, Lakshman Kumar. "Low-energy collision phenomena in free jet expansions: Molecular relaxation theory and ion-molecule rate studies." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185207.
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Theoretical and experimental development of a new kinetic method to measure the rate coefficients of ion-molecule reactions occurring in free jet expansions below 20K is presented. The method is successfully used to determine the temperature dependences of numerous bimolecular and termolecular ion-molecule reactions over the temperature range of 0.5-20K. A new theoretical method based on the generalized Boltzmann equation is developed to calculate macroscopic flow properties of pure molecular supersonic flows. The variation of the different temperature components, hydrodynamic speed and density of the free jet as a function of distance is presented assuming a Maxwellian anisotropic distribution function. This theory facilitates the kinetic analysis and the assignment of temperatures to the chemical reactions occurring in jets. Using the Boltzmann equation, the flow properties of a mixed atomic free jet expansion are also analyzed. The method is more general than previous treatments which assume a vanishingly small mole fraction for one component of the mixture. The presence of velocity slip arising from the difference in hydrodynamic speeds of the two components complicates this treatment. Expressions for the calculation of flow properties for an atomic mixture with an arbitrary composition are presented. Temperature dependences of the termolecular association rate coefficients for the reactions of, N₂⁺ + 2N₂, O₂⁺ + 2O₂ and NO⁺ + 2NO over the temperature range of 3-15K are presented. The results are discussed in the light of statistical phase space theory. For the reactions of N₂⁺ + 2N₂ and O₂⁺ + 2O₂ excellent agreement between theory and experiment is obtained. The kinetic analysis of NO⁺ + 2NO is complicated due to the competing charge transfer reaction. The observed temperature dependence for this reaction does not agree with the predictions of the statistical theory. The ternary association rate coefficients for the reaction, Ar⁺ + 2Ar, show a strong temperature dependence at very low temperatures (0.5-2.5K). Current statistical formulations cannot predict this temperature dependence and a comprehensive model for this reaction mechanism has yet to be developed. Three distinct temperature dependences are observed for the bimolecular reactions of N₂⁺ with CH₄, O₂ and n-H₂ at temperatures below 15K. Speculations are made regarding the interaction potential energy surfaces that may lead to the observed behaviors.
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McCrudden, Garreth. "Vector correlations in gas-phase inelastic collision dynamics." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:967fbe54-98a9-48e9-a0b2-707811804d7a.
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This thesis presents a joint experimental and theoretical study of vector correlations in the electronically, vibrationally, and rotationally inelastic collisions of simple molecules with rare-gas atoms. In the first instance, empirical and calculated data are presented for rotationally inelastic scattering in the NO(X)+Ar and ND3(X̃)+Ar systems at collision energies in the range 405-2210 cm-1. These experiments - the first to be conducted on a newly commissioned crossed-molecular beam machine - measured the k-k' correlation, i.e. that between the vectors describing the relative velocities before and after collision, respectively. The empirical data were subjected to rigorous comparison with both quantum-mechanical and quasi-classical trajectory (QCT) calculations. For both the NO(X)+Ar and ND3(X̃)+Ar systems, there is generally good agreement between experiment and theory at all four collision energies investigated. Two chapters of this thesis focus on the development of trajectory surface-hopping (TSH) QCT models of the OH(A, v = 0)+Kr and OH(A, v = 0)+Xe systems. Experimental data relating to scalar quantities (rotational energy transfer (RET) and electronic quenching) and to the j-j' correlation (which quantifies the depolarisation of the angular momentum of the OH(A) radical) are compared to variable-collision-energy TSH QCT calculations in which the length of the OH bond is fixed. The algorithms involve all three PESs of the OH(A/X)+Kr system, and the full range of electrostatic and roto-electronic mechanisms that couple them, for the first time. The most complete model succeeded in accounting for 93% of experimentally observed quenching. For the OH(A/X)+Xe system, coupling matrix elements were estimated from those of OH(A/X)+Kr, and the most complete model recovered 63% of experimentally observed quenching. This thesis also presents a novel theoretical study of rotationally inelastic dynamics in the OH(A, v = 1)+Kr system. Provisional results from adiabatic calculations in which the OH bond length is allowed to vary over the course of a trajectory are presented alongside experimental data that were reported previously. To date, these calculations continue to underestimate the extent of empirical RET data. Reasons for the observed discrepancy, and suggestions to resolve it, are outlined in detail.
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Handt, Jan. "Ab-initio molecular dynamics studies of laser- and collision-induced processes in multielectron diatomics, organic molecules and fullerenes." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-62279.
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This work presents applications of an ab-initio molecular dynamics method, the so-called nonadiabatic quantum molecular dynamics (NA-QMD), for various molecular systems with many electronic and nuclear degrees of freedom. Thereby, the nuclei will be treated classically and the electrons with time-dependent density functional theory (TD-DFT) in basis expansion. Depending on the actual system and physical process,
well suited basis sets for the Kohn-Sham orbitals has to be chosen. For the ionization process a novel absorber acting in the energy space as well as additional basis functions will be used depending on the laser frequency.
In the first part of the applications, a large variety of different laser-induced molecular processes will be investigated. This concerns, the orientation dependence of the ionization of multielectronic diatomics (N2, O2), the isomerization of organic molecules (N2H2) and the giant excitation of the breathing mode in fullerenes (C60).
In the second part, fullerene-fullerene collisions are investigated, for the first time in the whole range of relevant impact velocities concerning the vibrational and electronic energy transfer (\"stopping~power\").
For low energetic (adiabatic) collisions, it is surprisingly found, that a two-dimensional, phenomenological collision model can reproduce (even quantitatively) the basic features of fusion and scattering observed in the fully microscopic calculations as well as in the experiment.
For high energetic (nonadiabatic) collisions, the electronic and vibrational excitation regimes are predicted, leading to multifragmentation up to complete atomization.
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O'Rouke, Sheelagh Francesca Camille. "Theory of ion-atom collisions." Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334486.
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Gatchell, Michael. "Molecular Hole Punching : Impulse Driven Reactions in Molecules and Molecular Clusters." Doctoral thesis, Stockholms universitet, Fysikum, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-129523.
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When molecules are excited by photons or energetic particles, they will cool through the emission of photons, electrons, or by fragmenting. Such processes are often thermal as they occur after the excitation energy has been redistributed across all degrees-of-freedom in the system. Collisions with atoms or ions may also lead to ultrafast fragmentation in Rutherford-like scattering processes, where one or several atoms can literally be knocked out of the molecule by the incoming projectile before the energy can be completely redistributed. The resulting fragmentation pathways can in such knockout processes be very different from those in thermal processes. This thesis covers extensive studies of collisions between ions/atoms and isolated Polycyclic Aromatic Hydrocarbon (PAH) molecules, isolated fullerene molecules, or clusters of these. The high stabilities and distinct fragmentation channels make these types of molecules excellent test cases for characterizing knockout-driven fragmentation and the reactions that these processes can lead to. I will present experimental measurements for a wide range of energies and compare them with my own molecular dynamics simulations and quantum chemical calculations. In this thesis, I present an in-depth study of the role of knockout in the energetic processing of molecules and clusters. The competition between knockout and thermally driven fragmentation is discussed in detail. Knockout-driven fragmentation is shown to result in exotic fragments that are far more reactive than the intact parent molecules or fragments from thermal processes. When such reactive species are formed within molecular clusters efficient molecular growth can take place on sub-picosecond timescales. The cluster environments are crucial here because they protect the newly formed molecules by absorbing excess energy. This is a possible pathway for the growth of large PAHs, fullerenes, and similar carbonaceous complexes found in, for instance, the interstellar medium.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 1: Submitted.
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Shaffer, Nathaniel R. "Theory of collisional transport in ultracold neutral plasmas." Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6638.
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Ultracold neutral plasmas (UNP) are laboratory plasmas formed by the photoionization of a magneto-optically trapped and cooled gas. Because of their unusually low temperatures, UNPs are an example of a strongly coupled plasma, meaning that the potential energy of Coulomb interactions between particles is comparable to or greater than their thermal kinetic energy. In the field of strongly coupled plasmas, which also includes dense plasmas found in astrophysics and inertial confinement fusion experiments, there is a pressing need to better understand the collisional transport of matter, momentum, and energy between electrons and ions. The main result of this thesis is to demonstrate the existence of a new physical effect that significantly influences the electron-ion collision rates of strongly coupled plasmas. The essence of the effect is that the electron-ion collision rate depends explicitly on the sign of the colliding charges. This runs counter to both traditional plasma kinetic theory and modern extensions to strong coupling, all of which predict collision rates that do not depend on the sign of the electron-ion interaction. The effect is similar to a phenomenon observed charged-particle stopping known as the Barkas effect.
The existence of the Barkas effect in the electron-ion collision rate of strongly coupled plasmas is first demonstrated using molecular dynamics (MD) simulations. A non-equilibrium simulation methodology is developed to extract the electron-ion collision frequency from the relaxation of an induced electron drift velocity. The simulations are carefully designed to ensure that the relaxation process can be modeled with a constant relaxation rate, which facilitates comparison with theoretical predictions developed later in the thesis. The Barkas effect becomes apparent when these simulations are repeated with positrons in place of electrons. It is seen that the positron-ion collision rate is always lower than the equivalent electron-ion one, and that this charge-sign asymmetry widens rapidly with increasing electron (or positron) coupling strength.
It is hypothesized that the observed Barkas effect can be explained by accounting for plasma screening in the kinematics of binary electron-ion collisions. This is the main tenet of Effective Potential Theory (EPT), which assumes transport occurs through binary collisions governed by the potential of mean force. In order to apply EPT to electron-ion transport in UNPs, several new theoretical developments are made. First, it is demonstrated that EPT is able to accurately predict near-equilibrium transport in ionic mixtures as compared with equilibrium MD simulations. Next, a previously proposed model for the potentials of mean force in two-temperature positron-ion plasma is validated using a new two-thermostat MD methodology. Finally, EPT is applied to electron-ion transport in UNPs using a semi-analytic mapping between a two-component plasma and a screened one-component plasma system, which alleviates numerical difficulties in the theory associated with attractive interactions. The EPT predictions for the electron-ion and positron-ion relaxation rates are in excellent agreement with the MD simulations over the range of coupling strengths attained in present-day UNP experiments. EPT is thus shown to be the first transport theory for strongly coupled plasmas that accounts for the close-interaction physics that give rise to the Barkas effect in electron-ion transport.
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Gadea, Florent Xavier. "Theorie des hamiltoniens effectifs : applications aux problemes de diabatisation et de collision reactive." Toulouse 3, 1987. http://www.theses.fr/1987TOU30276.
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Etude approfondie sur la theorie des hamiltoniens effectifs et analyse de leurs applications aux methodes de diabatisation et au traitement des collisions reactives. Propositions pour le calcul des valeurs propres de l'hamiltonien par des methodes de perturbation ou iteratives, pour l'emploi d'hamiltoniens effectifs dans le calcul des surfaces quasi diabatiques et le traitement general des collisions reactives. Application a la reaction cs+h::(2) etudiee par les methodes ab initio pour la geometrie colineaire : surfaces de potentiel, sections efficaces et mecanismes predominants
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Niederhausen, Thomas. "Quantum dynamics in laser--assisted collisions, laser--molecule interactions, and particle--surface scattering." Diss., Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/313.
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Hornung, Balázs. "Rotational polarisation effects in the inelastic collisions of NO(X) and Ar." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:3fe4368b-6e16-469b-89bf-c8847203234e.
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Rotational polarisation effects have been investigated in the rotationally inelastic collisions of NO(X) and Ar by means of theoretical and experimental methods. Rotational polarisation describes the correlation between the k–k'–j' vectors, that is the initial and final relative velocities of the colliding partners and the final rotational angular momentum of the diatom, respectively. The simplest types of polarisation are the rotational orientation, or preferred sense of rotation, and the rotational alignment, or preferred plane of rotation. They are quantised by the renormalised polarisation dependent differential cross sections (PDDCSs) In this thesis the theoretical methods included exact quantum mechanical, quasi- classical trajectory and Monte Carlo classical hard shell calculations. Various features of the interaction potential influence differently the polarisation dynamics. The effects of attraction and soft repulsion were elucidated employing a number of differently modified potentials. The rotational alignment is primarily determined by a classical impulsive, or hard shell mechanism at a collision energy of 66 meV. The attractive and soft repulsive forces only perturb this underlying mechanism. On the other hand, the parity dependent oscillations of the open shell alignment moments are due to differences between the quantum mechanical differential cross sections. It has been shown the bigger the well depth compared to the collision energy, the less applicable becomes the classical hard shell model to describe rotational alignment. The quantum mechanical rotational alignment in the collisions of hard shells was also calculated. The classical and quantum mechanical hard shell models predict different rotational alignment. Nevertheless, the classical alignment is a good approximation to the exact quantum mechanical results. The rotational orientation is much more sensitive to the details of the interaction potential. It does not exist in the classical description of hard shell collisions, if the system exhibits certain symmetry properties. The attraction and finite range repulsion break this symmetry and leads to the molecule having a preferred sense of rotation. In general there is non-vanishing rotational orientation in the collisions of a hard shell in the framework of quantum mechanics. This is due to the finite spatial and temporal interaction of the colliding partners. Quantum mechanical interference effects also play an important role in this phenomenon. The rotational alignment was experimentally determined in the collisions of NO(X) and Ar at collision energy of 66meV with a hexapole state selective ion-imaging apparatus. An algorithm was developed based on the Fourier moment analysis to extract rotational polarisation information from the experimental ion images. It is fast and robust and can also be of used to simulate experimental images. This algorithm was used to retrieve the experimental renormalised PDDCSs ion images. The measurements confirmed that a classical, impulsive dynamics is mainly responsible for the rotational alignment in these collisions.
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Rossi, François-Noël. "Etude théorique des collisions non réactives entre atomes alcalins et molécules d'hydrogène ou de deuterium : Calcul et analyse des surfaces de potentiel, application aux transitions de structure fine du rubidium." Paris 13, 1986. http://www.theses.fr/1986PA132015.
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Calcul des courbes de potentiel adiabatiques pour les géométries colinéaires et perpendiculaires, à l'aide d'un pseudopotentiel dépendant du moment orbital électronique et d'une approche à deux centres; bon accord avec les calculs ab initio existants. Examen des différentes symétries de ces systèmes dans le formalisme de la théorie des groupes, afin d'étudier les valeurs propres et facteurs propres de l'hamiltonien électronique. Calcul quantique des sections efficaces relatives des transitions de structure fine de Rb induites par collision avec H(2) ou D(2). En tenant compte des niveaux rotationnels moléculaires, obtention d'un très bon accord avec les résultats expérimentaux et interprétation de l'effet isotopique
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Nova, Cássia Vanessa [UNESP]. "Aplicações da equação de Van Der Waals no estudo de colisões entre átomos e moléculas." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/99655.
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A teoria cinética dos gases tem como primeira aproximação o comportamento observado considerando o gás como tendo um comportamento ideal, isto é, pode ser modelado através da lei do gás ideal. As equações de estado conhecidas, como a equação do gás ideal e de van der Waals descrevem, dentro das aproximações do modelo, situações bastante diversas. Neste trabalho iremos utilizar a lei dos gases ideais, ou mais especificamente a implementação da Equação de van der Waals para o entendimento do fenômeno de colisões que entre átomos e moléculas
The kinetic theory of gases has a a first approximation the observed behavior considering the gas to have an ideal behavior, ie it can be modeled by the ideal bas law. The equations of state known as the ideal gas equation and Van der Waals describe, within the approximations of the model, very different situations. In this paper we use the ideal gas law, or more specifically the implementation of the Vann der Waals equation for understandign the phenomenon of collisions between atoms and molecules
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Coupier, B. "Studies towards the understanding of the effects of ionizing radiations at the molecular scales (20 to 150 keV H+/H + He Collisions; Dissociative Electron Attachment to Water)." Phd thesis, Université Claude Bernard - Lyon I, 2005. http://tel.archives-ouvertes.fr/tel-00012069.
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Ce travail s'inscrit dans le cadre d'études récentes pour la compréhension à l'échelle moléculaire des effets des rayonnements ionisants sur les systèmes biologiques, mises en oeuvre par le groupe IPM de l'IPNL en collaboration avec l'Institut für Ionenphysik de l'Université d'Innsbruck. Il est composé de deux parties. La première présente un nouvel ensemble de mesures des sections efficaces d'ionisation de l'hélium par impact de protons ou d'atomes d'hydrogène dans la gamme d'énergie d'intérêt pour la radiobiologie (20 à 150keV). Il s'agit de systèmes modèles d'intérêt pour la compréhension des phénomènes de base, et les collisions H + He ont fait l'objet, jusqu'à présent, de peu d'études utilisant les techniques de coïncidences. En outre, cette étude avec l'hélium a été faite dans l'intention de réaliser un test général de fonctionnement de l'appareillage avant d'aller vers des systèmes plus complexes. Des études similaires ont été ensuite réalisées en remplaçant la cible d'hélium par l'eau ou par des molécules d'intérêt biologique (Uracil, Thymine ...). La seconde partie de la thèse traite d'un autre type de radiations ionisantes que l'on peut voir comme une des conséquences secondaires des radiations étudiées dans la première partie. Des électrons de faible énergie (1 à 16eV) sont émis lors du bombardement de la matière par des protons ou des atomes d'hydrogène rapides; ces électrons ayant à leur tour des effets ionisants sur l'environnement. Une étude de l'attachement dissociatif des électrons sur l'eau a été entreprise à l'université d'Innsbruck, motivée par l'existence d'importants désaccords entre les précédentes études sur le même sujet. Le problème de la discrimination des ions à grande énergie cinétique dans le monochromateur trochoïdal utilisé pour cette étude a fait l'objet d'une attention particulière.
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Nova, Cássia Vanessa. "Aplicações da equação de Van Der Waals no estudo de colisões entre átomos e moléculas /." Bauru : [s.n.], 2012. http://hdl.handle.net/11449/99655.
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O Programa de Pós Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi
Resumo: A teoria cinética dos gases tem como primeira aproximação o comportamento observado considerando o gás como tendo um comportamento ideal, isto é, pode ser modelado através da lei do gás ideal. As equações de estado conhecidas, como a equação do gás ideal e de van der Waals descrevem, dentro das aproximações do modelo, situações bastante diversas. Neste trabalho iremos utilizar a lei dos gases ideais, ou mais especificamente a implementação da Equação de van der Waals para o entendimento do fenômeno de colisões que entre átomos e moléculas
Abstract: The kinetic theory of gases has a a first approximation the observed behavior considering the gas to have an ideal behavior, ie it can be modeled by the ideal bas law. The equations of state known as the ideal gas equation and Van der Waals describe, within the approximations of the model, very different situations. In this paper we use the ideal gas law, or more specifically the implementation of the Vann der Waals equation for understandign the phenomenon of collisions between atoms and molecules
Mestre
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Bryjko, Lilianna. "SA-CASSCF and R-matrix calculations of low-energy electron collisions with DNA bases and phosphoric acid." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/2608.
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The research presented in this thesis was carried out as part of a collaboration between the groups of Dr Tanja van Mourik at the School of Chemistry, University of St Andrews and Professor Jonathan Tennyson at the Department of Physics and Astronomy at University College London. This thesis presents State-Averaged Complete Active Space Self Consistent Field (SA-CASSCF) calculations on nucleic acid bases, deoxyribose and phosphoric acid H₃PO₄). In the case of uracil, for comparison, Multireference Configuration Interaction calculations were also performed. The SA-CASSCF orbitals were subsequently used in R-matrix electron scattering calculations using the close-coupling model. Of major importance for obtaining accurate SA-CASSCF results is the choice of the active space and the number of calculated states. Properties such as the electronic energy, number of configurations, excitation energy and dipole moment were considered in the choice of active space. Electron-collision calculations were performed on two of the most stable isomers of phosphoric acid, a weakly dipolar form with all OH groups pointing up and a strongly dipolar form where one OH group points down. A broad shape resonance at about 7 eV was found for both isomers. Ten-state close-coupling calculations suggest the presence of narrow, Feshbach resonances in a similar energy region. Elastic and electronically inelastic cross sections were calculated for both isomers. The R-matrix calculations on uracil were done by the group from UCL. R-matrix calculations are currently being done on guanine. Scattering calculations on the other DNA bases will be performed in the near future.
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Jenkins, Robert David. "Higher order energy transfer : quantum electrodynamical calculations and graphical representation." Thesis, University of East Anglia, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327601.
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Hervieux, Paul-Antoine. "Etude théorique et expérimentale de l'excitation des ions multichargés par impact électronique." Grenoble 1, 1992. http://www.theses.fr/1992GRE10183.
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Pour la premiere fois, la section efficace differentielle d'excitation d'un ion multicharge par impact d'electrons a ete mesuree. Dans une experience en faisceaux croises, la transition resonnante 3s-3p de l'ion sodiumoide ar#7#+ a ete etudiee pour une energie electronique incidente de 100 ev. En accord avec cette experience, nous avons calcule les sections efficaces differentielles et totales dans une approximation de born generalisee. Les sections efficaces experimentales sont en bon accord avec ces estimations theoriques. Nous avons montre que l'approximation de coulomb-born qui consiste a prendre les fonctions d'onde de coulomb pour fonctions d'onde du continuum, est justifiee meme pour les grands angles. Une approximation semi-classique a aussi ete developpee. Dans ce modele, le projectile se deplace sur une trajectoire coulombienne classique et l'excitation est traitee par la theorie des perturbations du premier ordre dependantes du temps. Cette approche est similaire a la theorie semi-classique de l'excitation coulombienne des noyaux. Deux resultats nouveaux se degagent de cette etude: a l'inverse de l'excitation des atomes qui est fortement piquee aux angles avant, la section efficace differentielle quantique et semi-classique est pratiquement nulle a zero degre, puis augmente jusqu'a un maximum. On peut estimer la position de ce maximum en egalant le temps de collision sur une trajectoire coulombienne et le temps caracteristique de la transition. Les sections efficaces totales semi-classiques sont pratiquement egales a celles obtenues dans l'approximation de coulomb-born. Ce resultat s'etend a d'autres multipoles et dans une large gamme d'energie, de transfert d'energie, et de charge ionique. Avec ce modele semi-classique, nous avons a notre disposition une methode simple pour obtenir, avec une bonne precision, les sections efficaces d'excitation d'ions multicharges
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Carrapatoso, Kléber. "Théorèmes asymptotiques pour les équations de Boltzmann et de Landau." Phd thesis, Université Paris Dauphine - Paris IX, 2013. http://tel.archives-ouvertes.fr/tel-00920455.
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Nous nous intéressons dans cette thèse à la théorie cinétique et aux systèmes de particules dans le cadre des équations de Boltzmann et Landau. Premièrement, nous étudions la dérivation des équations cinétiques comme des limites de champ moyen des systèmes de particules, en utilisant le concept de propagation du chaos. Plus précisément, nous étudions les probabilités chaotiques sur l'espace de phase de ces systèmes de particules : la sphère de Boltzmann, qui correspond à l'espace de phase d'un système de particules qui évolue conservant le moment et l'énergie ; et la sphère de Kac, correspondant à un système de particules qui conserve seulement l'énergie. Ensuite, nous nous intéressons à la propagation du chaos, avec des estimations quantitatives et uniforme en temps, pour les équations de Boltzmann et Landau. Deuxièmement, nous étudions le comportement asymptotique en temps grand des solutions de l'équation de Landau.