Tesi: "Inelastic dynamics"

1

Gates, Gary Anthony. "Inelastic scattering in gas-surface dynamics". Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358969.

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2

Marinakis, Sarantos. "The dynamics of inelastic and reactive bimolecular collisions". Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424735.

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3

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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4

Rusher, Cassandra Amelia. "Inelastic scattering dynamics of ammonia with small molecules". Thesis, Heriot-Watt University, 2016. http://hdl.handle.net/10399/3275.

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Crossed molecular beam velocity map imaging (VMI) is employed to state-selectively record the NH3 inelastic scattering products from collisions with a series of colliders; atomic Ar, diatomic D2, and the polyatomics CH4, C2H6 and C(CH3)4. The differential cross sections (DCSs) presented for NH3-Ar expand on the existing literature. The angular distribution of the scattering is found to exhibit a dependence on the angular momentum projection quantum number (k) of the NH3 product state in addition to the known dependency on the total angular momentum quantum number (J). It is found that for increasing k the total scattering into sideways and backwards angles (θ ≥ 60°) decreases. For the smallest molecular colliders D2 and CH4 co-excitation is observed. DCSs are presented for each NH3 product state and evidence of separate D2 co-excitation channels is obtained by a new extraction method for acquiring multiple DCSs from a single VMI image. The promotion of D2 into the JD2 = 3 rotational level exhibits an unusual propensity for excitation at larger impact parameters. It is proposed that this is due to interactions at larger distances with attractive regions of the potential energy surface (PES), at smaller impact parameters the steeper gradient of the PES inhibits coexcitation. The DCSs of NH3 scattering with methane, ethane and neopentane exhibit a striking similarity across all three systems and when comparing individual NH3 product states from a single collider. The DCSs are all dominated by forwards scattering angles (θ ≤ 60°) for all NH3 collisional excitations. The dominant mechanism suggested is a “tug-of- war” type trajectory, however calculations are required for confirmation of this interaction.

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5

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.

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6

Inoue, Rintaro. "Dynamics in Polymer Thin Films by Inelastic Neutron Scattering". 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/57278.

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7

Fabiani, Elisa. "Dynamics in strong glasses : an inelastic neutron scattering analysis". Université Joseph Fourier (Grenoble), 2005. http://www.theses.fr/2005GRE10031.

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Le but principal de cette thèse est d'effectuer une recherche systématique sur la dynamique des matériaux vitreux à des températures T beaucoup plus petites que la température de transition vitreuse Tg. Des études théoriques et expérimentales, exécutées pendant les deux dernières décennies sur différents aspects de l'état vitreux, ont établi un certain nombre de propriétés particulières qui concernent le dynamique à basse énergie et qui se manifestent dans la chaleur spécifique à basse température, dans la conductivité thermique, et dans la diffusion inélastique expérimentale. Certaines questions fondamentales dans ce domaine, relatives à la nature microscopique de la dynamique et à l'origine des caractéristiques "universelles" de la densité des états vibrationnels (VDOS) dans les verres, n'ont pas trouvé actuellement une réponse généralement admise. Afin d'expliquer certaines caractéristiques des verres, nous avons étudié deux verres forts, le quartz fondu (v-SiO2) et l'oxyde de germanium vitreux (v-GeO2). La technique utilisée est la dispersion inélastique des neutrons. Les études de ces échantillons avaient pour objectifs : i) le développement d'une nouvelle procédure pour extraire la VDOS à partir des systèmes cohérents en étendant l'approximation incohérente habituelle ; ii) l'étude de la diffusion quasiélastique de nos échantillons dans la région de très de basse fréquence ; iii) la comparaison des données de dispersion précédemment mentionnées, afin de calculer la fonction de couplage Raman C(w) et sa limite à basse fréquence ; iv) l'étude du v-GeO2 afin de prouver que les branches acoustiques longitudinales et transversales sont aussi définies dans le système vitreux
The main task of this thesis is to perform a systematic investigation of the dynamics of glassy materials at temperatures T much smaller than Tg, the glass transition temperature. Both theoretical and experimental studies performed over the last two decades on different aspects of the glassy state, have established a number of peculiar properties that concem low energy dynamics and manifest themselves in low temperature specifie heat, thermal conductivity, and inelastic scattering experiments. Sorne of the fundamental questions in this field, in particular about the microscopie nature of the dynamics and the origin of the "universal" features concerning the density of vibrational states in glasses, have not found a generally accepted answer. Ln order to explain some features of strong glasses, different systems have been investigated. Here we present new results on two strong glasses, vitreous silica (v-SiO2) and vitreous germania (vGeO2). The technique employed was inelastic Neutron Scattering (lNS). The studies of these sam pies have been done in order to : i) develop a new procedure to extract the density of states from coherent systems extending the usual Incoherent approximation ; (ii) study the QES of our samples at very low frequency range (in order to compare with Brillouin data and to asses a correlation with the mechanism causing the sound attenuation) ; (iii) compare of the previous scattering data above-mentioned, in order to calculate the Raman coupling function C(w) and its low frequency limit ; (iv) finally, investigate v-GeO2 to asses that both longitudinal and transverse acoustic branches are still somewhat defined also in glassy system

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8

Olgun, Asim. "The kinetics and dynamics of the liquid surface from molecular beam scattering". Thesis, University of Sussex, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388968.

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9

Saunders, Oliver Daniel. "Inelastic electron dynamics at clean and midified noble metal surfaces". Thesis, University of Bath, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538282.

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10

Jayne, Allen A. "Inelastic rotation requirements of two-span continuous bridge girders". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 7.08 Mb., p. 153, 2005. http://proquest.umi.com/pqdlink?did=1042538801&Fmt=7&clientId=8331&RQT=309&VName=PQD.

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11

Randall, Colin James. "State-resolved dynamics of electronically inelastic collisions of small free radicals". Thesis, University of Edinburgh, 1998. http://hdl.handle.net/1842/12833.

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The phenomenon of collision-induced electronic energy transfer in selectively excited diatomic radicals has been investigated experimentally. Direct laser excitation of initial rovibronic states and dispersed, temporally-resolved fluorescence analysis of both parent and collisionally populated levels has allowed the collisional encounter to be quantified at a state-specific level. Theoretical modelling of these results allows the form of the potential energy surfaces which control the dynamics to be established. In an extended series of experiments, collision-induced C²Δ-B²Σ⁺ transfer in the SiF radical has been investigated. It was observed that the product B²Σ⁺state vibrational distributions were well correlated with the Frank-Condon overlap between vibronic wavefunctions of the two states. Dominant channels were found to involve Δv=0, which corresponds to the energy defect of ~5000 cm^-1. Rotationally resolved investigation of the C²Δ, v=0→B²Σ⁺, v'=0 channel revealed a significant fraction of this energy to be released as product state rotation. A limiting impulsive model of the energy release reproduced the main features of the observed behaviour. Polarisation resolved investigation of the transfer event revealed significant depolarisation of the product B²Σ⁺ state compared to the initial C²Δ state. This observation was rationalised within two dynamically distinct models of rotational energy transfer. It is believed that all these observations may be explained by the valence-Rydberg nature of the electronic states involved. In a related set of experiments, novel measurements of collision-induced transfer between the A²Δ and B²Σ^- states of the CH radical have been obtained.

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12

Collins, Timothy L. D. "Inelastic rotational transfer differential cross-sections for Li2-rare gas collisions". Thesis, University of Sussex, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282082.

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13

Godfrey, Denise Caroline. "Reactive and inelastic scattering of CO and Ar from Cu(110)". Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389566.

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14

Lewis, Claire Anne. "Observable jets in deep inelastic scattering as a probe of small x dynamics". Thesis, Durham University, 1997. http://etheses.dur.ac.uk/5009/.

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The observation of the underlying small x dynamics arising from the resummation of large terms in In 1/x QCD descriptions of the gluon distribution have been searched for ill deep inelastic scattering experiments at the electron proton collider HERA since the early 1990's. It has been recognized that the first fully inclusive measurements of the proton structure function F2 are too inclusive to identify underlying dynamics. Less inclusive quantities need to be considered. In this thesis a modified form of the BFKL equation is derived which enables the structure of the gluon emissions to be studied in small x deep inelastic scattering. The equation incorporates the resummation of the virtual and unresolved real gluon emissions and is solved to calculate the number of small x deep-inelastic events containing 0,1,2...resolved gluon jets, that is jets with transverse momenta qr > µ. We study the jet decomposition for different choices of the jet resolution parameter to look for possible signatures of BFKL dynamics in the x dependence of the exclusive observable quantities of the n-jet contributions to F(_2).We also study the application of the BFKL equation to forward jet events at HERA. We calculate the rate of deep inelastic scattering events containing two forward jets adjacent to the proton remnants and compare with the production rate of only one forward jet - the so-called Mueller process. We obtain a stable prediction for this two to one jet ratio, which may serve as a measure of the BFKL vertex function.

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15

Sirmas, Nick. "Dynamics and Stability of Shock Waves in Granular Gases Undergoing Activated Inelastic Collisions". Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36568.

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The present work investigates the dynamics and stability of shock waves in granular gases. The problem was modelled for a piston propagating into a system of disks that can undergo inelastic collisions if an impact threshold is exceeded. The model was addressed numerically at the microscopic and macroscopic levels. The molecular dynamics methodology employed the Event-Driven Molecular Dynamics method, and the continuum model was formulated using the Navier-Stokes equations for granular gases with the transport terms of Jenkins and Richman and a modified cooling rate term. The inviscid steady state shock structure was derived and analyzed. The results indicated that a relaxing shock structure is expected for sufficiently strong shock waves. Beyond this limit the structure was shown to be independent of the initial energy, a finding similar to the strong shock approximation in molecular gases. One-dimensional simulations demonstrated that the molecular dynamics and continuum models yield similar evolutions and structures of the shock wave, validating the continuum description of this study. Two-dimensional results showed that sufficiently strong shock waves can exhibit multi-dimensional instability with high density non-uniformities and convective rolls within the structure, with the size of instabilities shown to scale with the relaxation length of the shock structure. Instabilities were observed with the continuum description only with the inclusion of statistical fluctuations to density mimicking the molecular model. The cases that were unstable were shown to be in a regime whereby statistical fluctuations can become important, following the description for this regime by Bird. Based on these findings, it is proposed that unstable shock behaviour can be observed for highly dissipative shock waves that yield short relaxation length scales, where fluctuations become important. The current work may shed light on unstable shock behaviour observed in dissipative gases, having implications for both granular media and molecular gases.

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16

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.

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17

Chadwick, Helen J. "Angular momentum polarisation effects in inelastic scattering". Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:474b04fa-4f50-4618-88ab-c85878723f2a.

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In this thesis, a joint experimental and theoretical investigation of the vector properties that describe the inelastic scattering of a diatomic radical with an atomic collision partner is presented. A particular emphasis is placed on those correlations that include the final rotational angular momentum, j', of the radical. The depolarisation of both NO(A) and OH(A) brought about through collisions with krypton has been studied, providing a measure of the j-j' correlation, where j is the initial rotational angular momentum associated with the diatom. The total depolarisation cross- sections for both collisional disorientation and disalignment have been measured using quantum beat spectroscopy, and modelled theoretically using quasi-classical trajectory (QCT) calculations. The agreement between experiment and theory for NO(A)-Kr is excellent, but is not observed for OH(A)-Kr under thermal conditions. This has been attributed to the importance of electronic quenching in OH(A)-Kr. The depolarisation cross-sections have also been determined at a higher collision energy for OH(A)-Kr where electronic quenching is less significant, and the experimental results are in better agreement with those obtained theoretically. The NO(A)-Kr depolarisation cross-sections fall with increasing rotational quantum number, N, whereas for OH(A)-Kr, they exhibit less of an N dependence. This trend is mirrored in the elastic depolarisation cross-sections, which have also been determined experimentally for OH(A)-Kr. The significantly attractive and anisotropic nature of the OH(A)-Kr potential energy surface (PES) accounts for these observations. The j-j' correlation is extended to include the initial (relative) velocity (k) in a new theoretical treatment of the k-j-j' correlation. The formalism developed is used with the results from the QCT calculations for NO(A)-Kr and OH(A)-Kr to provide further insight into the mechanism of depolarisation in the two systems. Collisions of NO(A) with krypton do not cause significant depolarisation due to their impulsive nature, and the projection of j onto the kinematic apse is conserved. In contrast, collisions of OH(A) with krypton effectively randomise the direction of j, again showing the influence of the anisotropic and attractive nature of the PES. However, the projection of j onto the kinematic apse is still conserved. The inelastic scattering of NO(X) with argon and krypton has also been investigated, using a crossed molecular beam apparatus. The initial Λ-doublet state of the NO(X) was selected using hexapole focussing, and the products of the collision detected using velocity mapped ion imaging. The state to state differential cross-sections (equivalent to the k-k' correlation, where k' is the final relative velocity) have been measured for collisions which conserve the initial spin-orbit level of the NO(X) with krypton. The same parity dependent effects were seen as have been observed previously for NO(X)-Ar. The collision induced alignment (equivalent to the k-k'-j' correlation) of NO(X) as a result of scattering with argon has also been determined experimentally. The results can be explained classically by considering the conservation of the projection of j onto the kinematic apse.

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18

Watts, Elizabeth Kathleen. "Quantum state-resolved studies of elastic and inelastic scattering of H₂ from Cu and Pd /". Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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19

Cunsolo, Alessandro. "Relaxation phenomena in the THz dynamics of simple fluids probed by inelastic X-ray scattering". Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10166.

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La dynamique a l'echelle atomique de differents exemples de fluides simples a ete etudiee dans le domaine de tres hautes frequences (thz) en utilisant la technique de la diffusion inelastique des rayons x avec une resolution de l'ordre du mev. L'etude experimentale est structuree naturellement en trois parties. Dans la premiere, le cas de la dynamique des fluides simples est traite, avec pour exemple, le neon tres au dela du point critique. Dans ce cas, le dynamique attendue doit etre proche de celle du cas simple des fluides a spheres dures, ou les interactions consistent en collisions mutuelles entre particules. La deuxieme partie concerne l'etude de la dynamique de systemes plus complexes, elle est illustree par l'exemple du neon cette fois en phase liquide. L'objectif de cette analyse est de differencier les effets lies aux interaction a plusieurs corps typiques des liquides, par rapport a l'etat supercritique. Dans la derniere partie, nous abordons l'etude de la dynamique des liquides pour lesquels existent des interactions spatiales a longue distance entre molecules. Le liquide choisit est l'eau en phase liquide. Pour ces trois etudes, un interet particulier a ete accorde a la caracterisation des phenomenes de relaxation. Plus specifiquement, nous montrons comment les phenomenes de relaxation evoluent avec le degre de connectivite croissant des systemes. Nous nous interessons a deux larges classes de phenomenes de relaxation : microscopiques et structurales. Les relaxations structurales sont liees a des processus cooperatifs par lesquels la structure locale, apres avoir ete perturbee par une fluctuation spontanee de densite, se rearrange vers une nouvelle position d'equilibre. Les relaxations microscopiques, d'un autre cote, ne sont pas cooperatives, elles impliquent une vibration atomique ayant une echelle de temps de l'ordre de 10 1 3s et ne dependent pratiquement pas de la temperature. Les premieres dominent les phenomenes observes dans l'eau, tandis que dans le cas du neon supercritique ou liquide, ce sont les relaxations microscopiques qui sont observees.

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20

Izzo, Maria Grazia. "High frequency dynamics of fluid binary mixtures". Doctoral thesis, Università degli studi di Trieste, 2010. http://hdl.handle.net/10077/3585.

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2008/2009
This thesis is aimed to the study of dynamics in binary fluid mixtures by means of inelastic scattering spectroscopies. Nowadays the understanding of these dynamics is still unsatisfactory. In particular, any model is able to adequately describe collective dynamics beyond the hydrodynamic limit. In such a low momentum (k) and frequency () transfer limit, the collective dynamics is characterized by a single (adiabatic) longitudinal acoustic mode accounting for sound propagation. At frequencies above the hydrodynamics ones a transition towards a decoupled dynamic regime is expected. This is characterized by two distinct modes, namely the slow (low-) and fast (high-) sounds. The microscopic mechanisms driving such a transition, so as the related macroscopic quantities, are still unclear, even in an heuristic point of view. In this work the collective dynamics of neutral and ionic mixtures are investigated with the aim to shed light in this debated issue. He/Ne mixtures have been studied by means of Inelastic X-ray Scattering (IXS) spectroscopy. Exploiting the lack of kinematic limitations peculiar of this technique, the high frequency (>THz) dynamics has been analyzed from the mesoscopic up to the high-k range, where the dynamic response of the system can be described using the Impulse Approximation (IA). This kind of study is of particular interest for disparate mass mixtures, since inefficient kinetic energy exchanges between light and heavy particles taking place on very short time scales are expected to greatly influence the phenomenology of the aforementioned dynamic decoupling. The prototype ionic mixture, RbF, also, has been investigated by means of Inelastic Neutron Scattering (INS) spectroscopy. Ionic mixtures are particularly suited to investigate the role played by optic-like excitations (related to concentration fluctuations) in the transition from the hydrodynamics to the decoupled regime. Indeed, these kind of excitations are expected to be emphasized because of the long range Coulomb interactions. Conversely at k’s enough high, i.e. k>k* with k* dependent on the values of the electric conduction coefficient and the adiabatic sound velocity, they are expected to behave like neutral binary mixtures. The study of molten RbF has been, then, focused on the characterization of collective dynamics in the transition region, which is more difficultly accessible by IXS because of instrumental limitations. IXS data on He0.8Ne0.2 mixture have been analyzed using a generalization of the viscoelastic function, which, in our knowledge, has been applied for the first time to this purpose. This kind of data analysis permitted to extrapolate the partial dynamical structure factors related to He-He, Ne-Ne and He-Ne density fluctuations. The adiabatic and high frequency sound velocity as well as the relaxation time associated to each mixture component has been calculated from fitting parameters. The analysis of the extrapolated relaxation times permitted to define, in the probed range, two k-region depending on the behavior of such quantity. At the higher k probed the relaxation times of single components can be well described by the respective single specie collision time, indicating a complete dynamics decoupling. At lower k, conversely, the relaxation times show a deviation to respect the collisional times. The study of the same mixture in three different thermodynamic conditions, revealed a common k trend of the single component relaxation times once proper normalization, made by means of kinetic parameters, has been done. An empirical expression has then been proposed. The result can be interpreted in the framework of ‘two temperature theory’, based on the assumption that in disparate mass binary mixtures inefficient kinetic energy exchanges induce a two step process for the relaxation of density fluctuations towards the thermodynamic equilibrium. These processes are characterized by two distinct timescales: the intra-specie collision time, where each specie subsystem reaches a condition of ‘local’ equilibrium associated with a ‘local’ temperature and a characteristic time for the equilibration of the microscopic temperatures to the thermodynamic temperature trough inter-specie collisions. A further corroboration of the above picture has been found from the analysis of IXS spectra in the IA region, which allowed extrapolating the momentum distribution functions of the specie subsets. An anomalous behavior has been noticed on the He momentum distribution function, i.e. the apparent temperature associated to the momentum distribution is about 40 K higher than the macroscopic one. This striking result can be straightforwardly interpreted as a fingerprint of the peculiar ‘two temperature’ equilibration process. INS experiment on molten RbF permitted to reveal the simultaneous presence of two dispersive collective modes in the transition region. The dispersive behavior (linear with k) and the characteristic energies permitted to exclude an optic-like nature for both excitations. The performed data analysis permitted also to extrapolate the value of the electrical conduction coefficient, founding a quite low value as compared with typical values of molten salts. An estimation of k* for the studied system emphasize the possibility that at the probed k it may be isomorphous to a neutral mixture. The observed phenomenology can be thus interpreted in terms of double sound propagation phenomenon, observed in rarefied non-ionic gaseous mixtures. Finally, an alternative interpretation of these experimental results can be qualitatively provided within the frame of the generalized collective mode approach. In this case the high frequency mode is identified with the extension of the adiabatic longitudinal sound mode beyond hydrodynamic limit that, in analogy to what observed in several fluids, follows a linear dispersion with an associated sound velocity larger than the adiabatic one. The low frequency mode could instead be associated with a propagating kinetic mode related to energy fluctuations (heat waves). In conclusion, an extensive analysis of high-frequency dynamics in binary mixtures has been reported. Particular emphasis has been devoted to the study of the sound decoupling phenomenon manifesting beyond the hydrodynamic region. The experimental results indicate that such a phenomenon is manifested in both neutral and ionic disparate mass binary mixtures. It can be related to microscopic dynamics, e.g. thermalization effects related to the inefficient kinetic exchange between lighter and heavier particles.
XXI Ciclo
1978

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21

Ziegler, Fabian. "Investigation of the Structure and Dynamics of Multiferroic Systems by Inelastic Neutron Scattering and Complementary Methods". Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://hdl.handle.net/11858/00-1735-0000-002E-E5A6-5.

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22

Hartnagel, Bryan A. "Inelastic design and experimental testing of compact and noncompact steel girder bridges /". free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9841147.

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23

Kargl, Florian. "The interplay of structure and microscopic dynamics in oxidic melts observed by means of inelastic neutron scattering". [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=978975618.

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24

Masciovecchio, Claudio. "The inelastic X-Ray scattering as a new technique to investigate the dynamics of glass-forming systems". Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10179.

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La principale motivation de cette these a ete l'etude de la dynamique collective des verres et des systemes aptes a former un verre a une echelle spatiale de l'ordre de la distance entre particules. Cette region n'etait pas facilement accessible avant le developpement de la technique de diffusion inelastique de rayons x (ixs), qui permet de mesurer directement le facteur de structure dynamique des particules dans les systemes. Afin d'etudier par ixs les excitations analogues a des modes phonons dans la region mesoscopique, une tres haute resolution en energie est necessaire. Dans ce contexte une importante realisation de cette these a ete la mise au point d'une technique pour la construction d'analyseurs spheriques adaptes a un spectrometre pour la diffusion inelastique de rayons x. Les analyseurs ainsi construits ont ouvert la possibilite d'effectuer des experiences de diffusion inelastiques de rayons x analysant les fluctuations de densite dans la matiere condensee. L'etude des modes collectifs dans les systemes aptes a former un verre a montre l'existence d'excitations inelastiques dont l'energie augmente avec l'impulsion transferee. L'observation d'une vitesse de groupe non nulle a prouve que les caracteristiques inelastiques observees sont encore dues a la propagation de modes analogues a des modes acoustiques. La comparaison avec des simulations de dynamique moleculaire a permis d'avoir une plus grande comprehension de la nature des vecteurs propres d'un systeme desordonne tel qu'un verre. Plus exactement, ces vecteurs propres sont bien representes par une onde plane et une composante aleatoire, et ils pourraient expliquer l'observation de l'exces en densite des etats vibrationnels dans les verres. Une etude de la dependance en temperature des modes a haute frequence dans le glycerol a permis de deduire le comportement en temperature de la vitesse du son a haute frequence, dans la phase liquide. Cette etude a montre que la ixs peut etre utilisee pour determiner experimentalement la dependance en temperature de la vitesse du son non-relaxee, ce qui constitue un parametre tres important pour toute approche hydrodynamique a la relaxation structurale dans les systemes aptes a former un verre.

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25

Eyles, Chris J. "An experimental and theoretical study of the dynamics of atom-molecule scattering". Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:d887db09-915e-4b3b-80e0-e9f1684518db.

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In this thesis, a joint experimental and theoretical study of the dynamics of atom- molecule collisions will be presented. The focus of this study will be conducted towards the precise, quantitative theoretical description of the collision dynamics in terms of the vectors k, k', j, and j' (the incoming and outgoing relative momenta associated with the collision, and the initial and final rotational angular momentum of the target diatom respectively) that define the collision, and on the experimental measurement of these vector correlations. Chapter 1 is introductory, providing an overview of the field of reaction dynamics, and the experimental and theoretical methods that exist to treat the collisions of atoms and molecules. This work focusses on the collisions of the spherically symmetric rare gas atoms Ar and He with the open-shell heteronuclear diatomic radicals NO and OH. In particular, the fully quantum state-to-state resolved differential cross-sections for the collisions of NO(X) with Ar (reflecting the k - k' vector correlation), and the collisional cross-sections for the depolarisation of the rotational angular momenta of the NO(A) and OH(A) radicals (reflecting the j - j' vector correlation) have been determined experimentally and theoretically, and the results have been discussed and interpreted in terms of the mechanistic aspects of the collision dynamics, and the features of the potential energy surface that give rise to these. In Chapter 2, the atom-molecule systems that constitute the subject of this work will be introduced in detail. The close-coupled quantum mechanical and quasi-classical trajectory scattering calculations performed as part of this work will be discussed in greater detail, providing a greater insight into molecular scattering theory. The explicit calculation of the quantities of interest (most significantly the differential cross-section, and the tensor/depolarisation cross-sections) will be presented for the quasi-classical and quantum cases, offering the most transparent definitions of these quantities. Finally the mathematical description of the spatial probability distribution of a single vector, a pair of correlated vectors, and three correlated vectors is described in detail, including a discussion of the quantum mechanical nature of the vectors in question. Chapter 3 describes the experimental measurement of the differential cross-sections for the collisions of NO(X) with Ar. A hexapole was used to select uniquely those NO molecules in the |Ω = 0.5; j = 0.5, f> quantum state, allowing full experimental quantum state-to-state selection for the first time. A crossed molecular beam apparatus with (1+1') resonantly enhanced multi-photon ionisation detection coupled with velocity mapped ion- imaging was employed to measure the differential cross-section, and the details of the experimental set-up are provided. The accurate extraction of the true, centre of mass frame differential cross-section from the laboratory frame information yielded by the experiment is something of an involved process, and much of this Chapter will be concerned with the development of a Monte Carlo method to achieve this end. In Chapter 4, the experimental and theoretical fully quantum state-to-state resolved differential cross-sections for the collisions of NO(X) with Ar are presented, having been measured for the first time. Full resolution of the initial parity of the rotational wave- function of the NO molecule has enabled the observation of parity dependent structures within the differential cross-section, and the origin of these structures has been investi- gated, employing quasi-classical, quantum mechanical and semi-classical methods in order to elucidate the mechanism by which they arise. Chapter 5 introduces the measurement of the collisional depolarisation of the rotational angular momentum of the diatom. Rate constants for the collisional depolarisation of j were measured by monitoring the time dependence of the amplitude of Zeeman and hyperfine quantum beats in the (1+1) laser induced fluorescence decays of an ensemble of NO(A) or OH(A) radicals in the presence of a series of background pressures of a collision partner. The creation and subsequent evolution of the polarisation of j induced by the absorption of polarised laser light is described, and the magnitude of this polarisation is linked to the amplitude of the quantum beat in the laser induced fluorescence decay. The extraction of the depolarisation cross-sections from the raw experimental data is discussed, and a Monte Carlo simulation of the experiment is described to account for any additional unwanted experimental factors that may contribute to the loss of polarisation of j. A formalism is also introduced that makes use of the tensor opacities to recover spin- rotation conserving and spin-rotation changing open-shell rotational energy transfer and depolarisation cross-sections from the intrinsically closed shell quasi-classical trajectory scattering calculations. In Chapter 6, the experimentally determined collisional depolarisation cross-sections for the collisions of NO(A) with He/Ar, and of OH(A) with Ar at collision energies of 39 meV/757meV are presented along with their theoretical counterparts. The relative magnitudes of the cross-sections are rationalised in terms of the potential energy surface over which the collision takes place, and the importance of spin-rotation conserving and spin-rotation changing transitions in the depolarisation process is assessed. A detailed study of the ensemble of quasi-classical trajectories is performed to determine the character of the various atom-molecule collisions, and to identify which conditions lead to the most efficient depolarisation of j. The relative importance of the potential energy surface and the collision kinematics is also assessed at this point. The results presented in this thesis thus investigate two complementary expressions of the collision dynamics, the k - k' and j - j' vector correlations, and encompass a variety of collision partners exhibiting vastly differing collision characteristics. As such, this work serves as an illustrative overview of atom-molecule scattering dynamics, containing both experimental and theoretical reflections of the collision dynamics, and relating this information back to the fundamentals of scattering theory.

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26

Um, Youngje [Verfasser], e Bernhard [Akademischer Betreuer] Keimer. "A study of lattice dynamics in iron-based superconductors by inelastic light scattering / Youngje Um. Betreuer: Bernhard Keimer". Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2014. http://d-nb.info/1049688813/34.

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27

PARMENTIER, ALEXANDRA. "FOLLOW THE WATER: an insight into proton quantum dynamics of selected phases of water by inelastic neutron scattering". Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2016. http://hdl.handle.net/2108/201939.

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The present PhD thesis stems from 36 months of intensive experimental investigation and data analysis of quantum dynamics of the hydrogen nucleus in various amorphous solid states (AIs) and supercritical phase (SCW) of water by inelastic neutron scattering. This doctoral eﬀort places this work into the apparently inexhaustible stream of studies on water, at the same time oﬀering an evidence of the role of density in shapingthesingle-particlepotential-energysurfaceintermsofcurvatureandanharmonicity,ashighlightedbyarecenthigh-impactpublicationinJ. Phys. Chem. Lett. [1]. The layout of the monograph has been thought for a broad audience, with an eye to making it both agile and exhaustive. After a brief introduction on the why and how of water and neutron spectroscopy, two separate chapters are dedicated to the properties of amorphous ices and the supercritical ﬂuid, followed by the presentation of the fundamentals of inelastic (INS) and deep-inelastic (DINS) neutron techniques, and a sketch of the instrumentation employed, which is functional to the full understanding of the development of data reduction and analysis. Thesubsequentchapteronthepotentialofmeanforce(PMF)introducesanalternativeandpossiblyeasier-to-managewaytointerpretDINSoutputs. Thearrangement of related data and their interpretation into a scientiﬁc paper for a special issue of Front. Phys. is currently afoot. The work closes with a clean report of experimental results and relative discussion, which allows for inferring new insights into the function and eﬀects of the H-bond environmentthemoleculesareimmersedin, aswellaspicturingfutureinvestigation scenarios. All INS and DINS experiments described in the following sections were performed at MARI and VESUVIO spectrometers, respectively, both located at ISIS Neutron and Muon Pulsed Source at the Rutherford Appleton Laboratory in the UK, with later data analysis and interpretation developed at the Department of Physics of Tor Vergata University of Rome, Italy. Theexperimentalworkwasaccompaniedbytheparticipationbypostercontribution in the 2013 International Conference on Neutron Scattering in Edinburgh, UK, the VI Workshop in eV Neutron Spectroscopy (2014) in Abingdon, UK, and the 2016 Erice School (’Water and Water Systems’) held in Erice (TP), Italy, and promoted by the School of Neutron Scattering (SoNS) entitled to Francesco Paolo Ricci.The second meeting called for my personal involvement into the coordination of the ﬁnal scientiﬁc discussion, which is currently included in the proceedings of the conference [2–4]. A fruitful introduction to the PhD route was for sure the pre-doctorate course on general neutron scattering held by ILL in summer 2012 (Giornate Didattiche). As to present, I am about to start a full-immersion training as a McStas professional user, in order to participate in the development of the VESPA Project at the European Spallation Source (ESS). A parallel collaboration is in progress with a team based in Sapienza University of Rome in order to investigate anomalous transport properties of ultraconﬁned water by quasi-elastic neutron scattering (QENS) [5] and other spectroscopic techniques.

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28

Gordon, Sean Dennis Steven. "Two and three vector correlations in the rotationally inelastic scattering of state-selected NO(X)". Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:ec0f133b-b2ef-482c-b90c-59fc313c8baa.

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In this thesis, an experimental and theoretical study of two and three vector correlations in the inelastic scattering of NO(X) with various rare gas atoms is presented. Vector correlations for a selection of rare gas systems were determined experimentally, and the observations were interpreted using a variety of classical and quantum mechanical models. The experiment is able to provide state-to-state resolution of the dynamics by means of an electrostatic hexapole and 1+1' resonantly enhanced multi-photon ionisation (REMPI). The simplest vector correlation of interest is the differential cross section (DCS), given by the k-k' correlation. The DCSs were determined experimentally for the NO(X)--Kr and NO(X)--Xe collision systems, both characterised by the relatively deep (≈140cm^-1) attractive well and large extent of the attractive potential. The agreement between the experimental angular distributions and quantum mechanical DCS is very good for both systems. Classical calculations fail to correctly reproduce the form and magnitude of the DCS for either system, reflecting the inherently quantum mechanical nature of the collision. The classical calculations do however provide mechanistic insight into regions where the attractive part of the potential plays an important role in determining the dynamics. In order to investigate narrow angular features in the forward scattered direction, several experimental improvements to molecular beams and the detection ion-optic stack were made. Investigation into these structures revealed a strong contribution from molecular diffraction into the classical shadow of the NO(X), and the simple Fraunhofer model revealed a preference for scattering from an individual m→m' sub-state. Such measurements are in a region of the DCS where scattering is forbidden classically, and reveal the purely quantum nature of the collision interaction in the forward scattered direction. The low order k-k' correlation was then extended by using linearly or circularly polarised laser excitation. The interaction of the light with the molecular dipole allows the measurement of the k-k'-j' correlation. When linearly polarised light was used for the excitation laser, two of the rank two p^{2}_q(θ) renormalised polarisation dependent differential cross sections (PDDCSs), which describe rotational alignment, were obtained. With circularly polarised light, the rank one p^{1}_1-(θ) renormalised PDDCSs describing rotational orientation were determined. The collision induced alignment in NO(X)--Xe scattering was found to be well reproduced by classical and impulsive theories, highlighting the fact that the alignment is dominated by the propensity for the projection of j onto the kinematic apse to be conserved. The attractive part of the potential does augment the alignment renormalised PDDCSs, and this is most evident in states with strong features of the attractive part of the potential such as ℓ-type rainbows. The orientation is more strongly influenced by the attractive part of the potential and is also influenced by parity. In addition to the parity effect, there exist two limiting classical mechanisms which govern the orientation, one caused by attraction and the other repulsion. Finally, the bond axis of the NO(X) can be oriented by means of hexapole state selection combined with adiabatic orientation using a set of guiding rods. The integral steric effect, an r-k correlation, was measured for the NO(X)--Kr and NO(X)--Ar spin-orbit changing systems. There are large oscillations in the sign of the steric asymmetry which occur for scattering with the various rare gases. There are also large differences between the rare gases as the potentials become more attractive, and more isotropic. The steric asymmetry is well reproduced by quantum mechanics, however, a classical mechanism becomes dominant at high Δj.

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29

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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30

Laurent, Sébastien. "Dynamics and stability of a Bose-Fermi mixture : counterflow of superfluids and inelastic decay in a strongly interacting gas". Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEE023/document.

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La compréhension des effets des interactions dans un ensemble de particules quantiques représente un enjeu majeur de la physique moderne. Les atomes ultra-froids sont rapidement devenus un outil incomparable pour étudier ces systèmes quantiques fortement corrélés. Dans cette thèse, nous présentons plusieurs travaux portant sur les propriétés d’un mélange de superfluides de Bose et de Fermi créé à l’aide de vapeurs ultra-froides de ⁷Li et de ⁶Li. Nous étudions tout d'abord les propriétés hydrodynamiques du mélange en créant un contre-courant entre les superfluides. L'écoulement est dissipatif uniquement au dessus d'une vitesse critique que nous mesurons dans le crossover BEC-BCS. Une simulation numérique d’un contre-courant de deux condensats permet de mieux comprendre les mécanismes sous-jacents mis en jeu dans la dynamique. En particulier, l'étude numérique fournit des preuves supplémentaires que l'origine de la dissipation dans nos expériences est liée à l'émission d'excitation élémentaires dans chaque superfluide. Finalement, nous nous intéressons aux pertes inélastiques par recombinaison à trois corps qui peuvent limiter la stabilité de nos nuages. Ces pertes sont intimement liées aux corrélations à courte distance présentes dans le système et sont ainsi connectées aux propriétés universelles du gaz quantique. Cela se manifeste notamment par l’apparition de dépendances en densité ou en température inusuelles du taux de perte lorsque le système devient fortement corrélé. Nous démontrons cet effet dans deux exemples où les interactions sont résonantes, le cas du gaz de Bose unitaire et celui de notre mélange de superfluides Bose-Fermi. Plus généralement, nos travaux montrent que ces pertes inélastiques peuvent être utilisées pour sonder les corrélations quantiques dans un système en fortes interactions
Understanding the effect of interactions in quantum many-body systems presents some of the most compelling challenges in modern physics. Ultracold atoms have emerged as a versatile platform to engineer and investigate these strongly correlated systems. In this thesis, we study the properties of a mixture of Bose and Fermi superfluids with tunable interactions produced using ultracold vapors of ⁷Li and ⁶Li. We first study the hydrodynamic properties of the mixture by creating a counterflow between the superfluids. The relative motion only exhibit dissipation above a critical velocity that we measure in the BEC-BCS crossover. A numerical simulation of counterflowing condensates allows for a better understanding of the underlying mechanisms at play in the dynamics. In particular, this numerical study provides additional evidence that the onset of friction in our experiment is due to the simultaneous generation of elementary excitations in both superfluids. Finally, we consider the inelastic losses that occur via three-body recombination in our cold gases. This few-body process is intimately related to short-distance correlations and is thereby connected to the universal properties of the many-body system. This manifests as the apparition of an unusual dependence on density or temperature in the loss rate when increasing the interactions. We demonstrate this effect in two examples where interactions are resonant: the case of a dilute unitary Bose gas and the one of impurities weakly coupled to a unitary Fermi gas. More generally, our work shows that inelastic losses can be used to probe quantum correlations in a many-body system

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31

Liu, Yun 1973. "Studies of structure and dynamics of biological macro-molecular assemblies by low angle neutron diffraction and inelastic X-ray scattering". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/34438.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2005.
Includes bibliographical references (leaves 141-148).
This thesis is organized into two parts which focus on the studies of the dynamic structure factor and static inter-particle structure factor respectively. In the first part, we have measured and analyzed the dynamic structure factors of aligned 40 wt% calfthymus Na-DNA molecules with the inelastic X-ray scattering (IXS). In the second part, we have developed a new efficient method to calculate the inter-particle structure factor in a simple fluid interacting with a two-Yukawa term potential and apply it to study the kinetic phase diagram and analyze the small angle neutron scattering (SANS) intensity distribution of colloidal systems. By analyzing the dynamic structure factor measured with IXS, the phonon dispersion relations of 40 wt% calf-thymus Na-DNA with different counterion atmosphere are constructed. It is found that the addition of extra counterions will increase phonon damping at small scattering wave vector, Q. At the intermediate Q range (12.5 nm- < Q < 22.5 nm-l), it may even overdamp the phonon so that the phonon feature can not be extracted from the IXS spectra. The measured sound speed is 3100m/s, which is much higher than the sound speed, - 1800m/s, obtained by Brillouin light scattering. This difference shows that the atoms of DNA molecules are closely coupled to the surrounding water molecules.
(cont.) Therefore, the different dynamic response of water molecules in different Q range affects the overall dynamic response of the hydrated DNA molecules. By analyzing the IXS spectra, the intermediate scattering function is extracted and shows a clear two step relaxation with the fast relaxation time ranging from 0.1 to 4 ps and the slow relaxation time ranging from 2 to 800 ps. In order to understand the phase behavior and the interactive potential of a colloidal system, we have developed a new and efficient method to calculate the inter-particle structure factor of a simple fluid interacting with a two-Yukawa term potential. We have applied this method to study the kinetic phase diagram of a system interacting with a short-range attraction and a long-range repulsion. A new glass phase, cluster glass, is determined through the theoretical analysis by the mode coupling theory (MCT). The SANS intensity distribution of cytochrome C protein molecules in solutions is measured and analyzed with our method. A sharp rising intensity at very low Q value has been consistently observed, which is named zero-Q peak. The existence of the zero-Q peak implies that a weak long-range attraction between protein molecules in solutions exists and has a even longer range than the electrostatic repulsion.
by Yun Liu.
Ph.D.

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32

PANTALEI, CLAUDIA. "Single-particle dynamics of helium mixtures and 4He in nanometric confinement". Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2008. http://hdl.handle.net/2108/473.

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Scopo di questa tesi e' lo studio, tramite Deep Inelastic Neutron Scattering, della dinamica microscopica di due differenti sistemi di elio, a bassa temperatura (circa 2 K): una miscela isotopica (nella fase fluida e vicino al punto di melting) e 4He in in confinamento nanometrico. L'interesse per l'elio, gia' dai primi decenni del `900, nasce dalla sua unica proprieta': e' l'unico elemento in natura a non avere una fase solida allo zero assoluto. A basse temperature, quindi, presenta effetti quantistici, normalmente trascurabili in altri sistemi fisici, che nelle stesse condizioni solidificano. l'elio e' quindi l'unico banco di prova per i modelli teorici quantistici, in particolare per lo studio di bosoni e fermioni interagenti. In questo contesto, molti esperimenti sono stati effettuati sull'elio, sia nella fase liquida che solida. Misure su 3He e 4He hanno mostrato che l'energia cinetica dei liquidi puri dipende dalla densita' del sistema, crescendo con una diminuzione del volume molare. D'altra parte, la dinamica microscopica delle miscele mostra un differente comportamento rispetto al 3He e 4He puri: l'energia cinetica media dell'isotopo piu' leggero, a volumi molari maggiori di 25cm3/mole, sembra essere indipendente dal volume molare e dalla concentrazione. Questo andamento potrebbe essere spiegato da effetti quantistici, come gli effetti di scambio. Nella prima parte del presente lavoro si e' investigata la dinamica delle miscele per volumi molari tra 22cm3/mole e 25cm3/mole, e gli esperimenti compiuti hanno mostrato che in questo range di volumi molari l'energia cinetica media degli atomi di 3He risulta dipendente dal volume molare, aumentando fino ad avere un valore corrispondente a quello del 3He puro. Recentemente sono state compiute anche misure per studiare l'influenza di un confinamento sull'elio. Esperimenti su 4He, adsorbito in superfici piane o substrati porosi, hanno rivelato un elevato aumento nel valore dell'energia cinetica. Questo comportamento e' stato attribuito alla localizzazione degli atomi di He dovuta al potenziale di interazione He-substrato, che influenza fortemente i primi due o tre layers. Questi tipi di effetti possono essere studiati confinando 4He in pori cilindrici con differenti diametri dei pori. Scopo della seconda parte di questa tesi e' stata appunto quella di determinare l'energia cinetica media degli atomi di 4He adsorbiti in sistemi nanoporosi a geometria cilindrica (Xerogel) con due diametri medi dei pori, di 24ºA 160ºA, per valutare la dipendenza della dinamica a singola particella con la dimensione dei pori e con il tipo di geometria. Le misure sono state effettuate a T=2.5K, a pressione di vapor saturo e con un riempimento dei pori del 95%. L'esperimento ha mostrato che l'energia cinetica del 4He nei pori e' maggiore rispetto a quella del 4He liquido nelle stesse condizioni. I risultati sono stati interpretati tramite un modello teorico, secondo il quale gli atomi si posizionano in anelli concentrici, stratificando layer per layer, e con un'energia cinetica dipendente dal rapporto tra il diametro del poro e quello dell'atomo di elio.
The aim of this thesis work is the study, by means of Deep Inelastic Neutron Scatter- ing, of the microscopic dynamics of two different helium systems at low temperature (T=2K): an isotopic helium mixture (in the fluid phase and near the melting point) and a system of 4He in nanometric confinement. The interest in the helium, from the first decades of 1900, is due to its unique features: it is the only element in nature that doesn't have a solid phase at absolute zero. Thus, at low temperatures it presents quantum effects, usually negligible in other physical systems that in this condition crystallise. The helium is thus the unique test-bed for theoretical quantum models, in particular for studying the interacting boson (4He) and fermion (3He) systems. Moreover, if in 4He are added some atoms of 3He it is possible to derive important information about the interplay of these two statistics. In this context, several experiments on liquid and solid helium have been performed. Measurements on pure 3He and 4He have shown that the mean kinetic energy of pure liquids depends on the density of the system and increases decreasing the molar volume. On the other hand, the microscopic dynamics of helium mixtures reveals quite a different picture with respect to pure 3He and 4He: the mean kinetic energy of the light isotope, above a molar volume of 25cm3/mole, shows a remarkable independence from molar volume and concentration. This behaviour could be explained by quantum effects, such as exchange effects. The first part of the present work deals with the experiments performed to investigate the dynamics of the mixtures from 22cm3/mole to 25cm3/mole and shows how, at these low molar volumes, the mean kinetic energy of 3He starts again to be strongly dependent on the molar volume, increasing until reaching, at 22.7cm3/mole, the corresponding value of pure helium. Recent measurements have been also performed to investigate the influence of confinement on helium. Experiments on 4He, adsorbed in flat surface or slit geometry porous substrates, have shown a large increase in helium mean kinetic energy. This has been attributed to the strong localisation effects induced by the helium-substrate interaction potential, which mainly influence the firsts two or three adsorbed layers. Such effects can be also investigated by confining 4He atoms in cylindrical pore geometries and by studying their dynamics as function of pore size. Aim of the second part of the thesis has been the determination of the single particle mean kinetic energy of 4He adsorbed in cylindrical silica nanopores (Xerogel) having two different pore diameters, namely, 24 ºAand 160 ºA, and to evaluate the dependence of single- particle dynamics on pore sizes, layer coverage, and confining system geometry. The measurements have been performed at a temperature of T=2.5K, saturated vapour pressure, and 95% volume filling. Significant changes in the values of the single particle mean kinetic energy are found: they are remarkably higher than the value of normal liquid 4He at the same conditions. The results are interpreted in terms of a model in which 4He atoms are arranged in concentric annuli along the cylindrical pore axis, growing layer-by-layer and with the mean kinetic energy mainly dependent on the ratio between the atomic diameter and the pore diameter.

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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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Ziegler, Fabian [Verfasser], Götz [Akademischer Betreuer] Eckold, Götz [Gutachter] Eckold e Dietmar [Gutachter] Stalke. "Investigation of the Structure and Dynamics of Multiferroic Systems by Inelastic Neutron Scattering and Complementary Methods / Fabian Ziegler ; Gutachter: Götz Eckold, Dietmar Stalke ; Betreuer: Götz Eckold". Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://d-nb.info/1179449266/34.

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35

Angelini, Roberta. "Study of the high frequency dynamics in hydrogen bonded liquid systems by inelastic x-rays scattering : the case of hydrogen fluoride and (HF)x(H2O)1-x solutions". Université Joseph Fourier (Grenoble), 2003. http://www.theses.fr/2003GRE10036.

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La dynamique aux hautes fréquences de deux systèmes à liaison hydrogène, l'acide fluorhydrique (HF) et les solutions aqueuses (HF)x (H2O)1-x, a été étudiée par diffusion inélastique des rayons X. La comparaison avec des simulations de dynamique moléculaire montre la présence de deux processus de relaxation actifs dans 1 'HF avec un temps de relaxation inférieur à la picoseconde. Ce scénario, proche de celui de l'eau liquide, suggère que les liquides à liaison hydrogène ont un comportement similaire à des systèmes différents (les liquides simples et ceux aptes à former des verres). Ceci indique que ces deux processus de relaxation possèdent un caractère universel propre à l'état liquide. Etant donné que la principale différence entre l'HF et l'eau concerne l'organisation spatiale des agrégats de molécules reliées par liaison hydrogène, nous avons appliqué notre recherche aux solutions (HF)x (H2O)1-x afin de déterminer l'évolution de la dynamique au passage d'un liquide à l'autre
The high frequency dynamics of two hydrogen bonded liquid systems: hydrogen fluoride (HF) and (HF)x (H2O)1-x solutions has been studied by inelastic X-ray scattering. The comparison with existing molecular dynamics simulations shows the existence of two relaxation processes active in HF with characteristic time-scales in the sub-picosecond range (<10-12 s). The observed scenario, similar to that found in liquid water, suggests that hydrogen bonded liquids behave similarly to other very different systems as simple and glass forming liquids, thus indicating that these two relaxation processes are univers al features of the liquid state. Since the main difference between hydrogen fluoride and water is nature of the hydrogen bond network: uni-dimensional for the former, three-dimensional for the latter, we addressed our study to the (HF)x (H2O)1-x solutions to determine the evolution of the dynamics from the phenomenology of one liquid to that ofthe other

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Gonzalez, Jose Ignacio. "Quantum Optoelectronics: Nanoscale Transport in a New Light". Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-04062006-110542/.

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Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2006.
Dr. C. P. Wong, Committee Member ; Dr. C. David Sherrill, Committee Member ; Dr. Thomas M. Orlando, Committee Member ; Dr. Mostafa A. El-Sayed, Committee Member ; Dr. Robert M. Dickson, Committee Chair.

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Beauvois, Ketty. "Etude de la dynamique de l'3He liquide et de l'4He superfluide par diffusion inélastique de neutrons". Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY094/document.

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L’étude des corrélations dans les fluides quantiques est abordée dans cette thèse par le biais de mesures neutroniques de leurs excitations élémentaires. Nos recherches sont motivées par les théories récentes qui permettent désormais de décrire ces excitations jusqu’à des vecteurs d’onde atomiques. Par ailleurs, les nouvelles performances du spectromètre temps de vol IN5 de l’ILL offrent la possibilité de réaliser des mesures précises dans une large gamme d’énergie et de vecteur d’onde. Dans le cas de l’4He, l’isotope bosonique, les mesures de diffusion inélastique ont été réalisées à très basse température, de la pression de vapeur saturante jusqu’à la solidification. Les relations de dispersion des excitations élémentaires correspondantes ont été obtenues avec une grande précision. A des énergies supérieures, nous avons observé dans le facteur de structure dynamique une réponse de multi-excitations très fortement structurée, caractérisée par des seuils correspondant à l’interaction entre les modes élémentaires. En particulier, nous avons observé un phonon “fantôme” associé à l’interaction phonon-phonon. Nos mesures dans l’4He superfluide confirment qualititativement les prédictions de la théorie dynamique à N-corps (2015) et même quantitativement jusqu’à une énergie de 2 meV. Les études effectuées dans le cas de l’3He ont été menées jusqu’à des températures bien inférieures à 100 mK dans une cellule spécialement conçue. Les mesures inélastiques sur cet isotope fermionique ont permis de déterminer avec une grande précision les modes collectifs, zéro-son et paramagnon, ainsi que la bande particule-trou. Couvrant une région encore jamais explorée, elles nous ont permis de confirmer la présence prévue par la théorie d’une excitation de type rotonique dans l’3He liquide massif. Ce mode reste ici confiné dans la bande particule-trou, contrairement au cas de l’3He bidimensionnel. L’ensemble de nos mesures apporte une vision complète du facteur de structure dynamique de ces systèmes modèles pour les bosons et les fermions en interaction, depuis le régime de quasi-particules de Landau et des multi-excitations, jusqu’à la limite des hautes énergies où la dynamique rejoint celle des particules indépendantes
The effect of correlations in quantum fluids is investigated in the present work by inelastic neutron scattering measurements of their elementary excitations.Recent theories provide us with a detailed description of the dynamics up to atomic wave vectors. In addition, the recent improvement of the time-of-flight IN5 spectrometer at the ILL opens new experimental possibilities in terms of neutron flux and resolution, as well as accessible energy and wave vector ranges. In the case of 4He, the bosonic isotope, the neutron measurements have been performed at very low temperatures, from the saturated vapor pressure up to the melting curve. The dispersion relations of the corresponding elementary excitations have been accurately determined. At higher energies, we observe in the dynamic structure factor a highly structured multi-excitation response, characterized by sharp thresholds due to the coupling of elementary excitations. In particular, we observe a ghost phonon related to phonon-phonon coupling. Our measurements on superfluid 4He confirm the predictions of the dynamic many body theory (2015), the agreement being quantitative up to an energy of 2 meV. The investigations on normal liquid 3He were carried out at temperatures well below 100 mK in a cell specially designed for this purpose. Ourmeasurements on this fermionic isotope yield a high precision determination of the collective modes, zero-sound and paramagnon, as well as the particle-hole band. Since they also cover an unexplored region, we were able to confirm the theoretical prediction of a roton-like excitation in bulk liquid 3He. This mode remains within the particle-hole band, contrarily to the case of two-dimensional 3He. A broad vision of the dynamics of interacting Bose and Fermi systems, going from the Landau quasi-particles and multi-excitations regimes up to the high-energy limit, where the independent particle dynamics is recovered, emerges from our work

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Seel, Andrew G. "Incoherent neutron scattering studies of select inorganic systems : I. Nuclear momentum measurements of multiple masses, II. The dynamics of coordinated ammonia in zeolite A". Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:48e7a487-b203-46d6-9bb3-2866b1d98f1b.

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Spectroscopic measurements are detailed within this thesis, utilising incoherent neutron scattering to examine the dynamics of various condensed-matter systems, from nanosecond to sub-femtosecond timescales. The body of this work is divided into two distinct areas of research. I. Nuclear Momentum Measurements of Multiple Masses Deep inelastic neutron scattering (DINS) is used to probe the nuclear momentum distributions and kinetic energies of individual atomic species in sodium hydride (both in bulk and as nanoparticulates within a silica matrix), enriched lithium-7 fluoride and lithium tetra-ammoniate. Extension of DINS to examine heavier (M>4amu) nuclei is detailed, accomplished by the application of a simple stoichiometric fixing technique within the standard DINS theory and analysis protocols. The validity and accuracy of such simultaneous measurements are discussed. II. The Dynamics of Coordinated Ammonia in Zeolite A Inelastic neutron scattering (INS) and quasielastic neutron scattering (QENS) are utilised in the examination of vibrational and stochastic dynamics of the ammonia molecule, as coordinated to the internal surface of a zeolite host. Both sodium and copper-exchanged forms of zeolite-A are studied, with proton-weighted, low energy phonon-modes and rotational processes being observed and assigned.

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39

Lorenz, Wolfram [Verfasser], Bernd [Akademischer Betreuer] Büchner e Rüdiger [Akademischer Betreuer] Klingeler. "On the Spin-Dynamics of the Quasi-One-Dimensional, Frustrated Quantum Magnet Li2CuO2 : Studies by means of Inelastic Neutron Scattering and Thermodynamic Methods / Wolfram Lorenz. Gutachter: Bernd Büchner ; Rüdiger Klingeler. Betreuer: Bernd Büchner". Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://d-nb.info/1067190074/34.

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40

Lorenz, Wolfram E. A. [Verfasser], Bernd [Akademischer Betreuer] Büchner e Rüdiger [Akademischer Betreuer] Klingeler. "On the Spin-Dynamics of the Quasi-One-Dimensional, Frustrated Quantum Magnet Li2CuO2 : Studies by means of Inelastic Neutron Scattering and Thermodynamic Methods / Wolfram Lorenz. Gutachter: Bernd Büchner ; Rüdiger Klingeler. Betreuer: Bernd Büchner". Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-71010.

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41

Ruta, Béatrice. "Les propriétés vibrationnelles des verres : une étude expérimentale dans la région de transition entre le régime microscopique et macroscopique". Grenoble, 2010. http://www.theses.fr/2010GRENY034.

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Une des questions les plus ambitieuses dans la Physique de la Matière Condensée concerne la compréhension des propriétés vibrationnelles des verres. En particulier, une anomalie présente dans la densité d’états vibrationnels (VDOS) à des énergies de quelques meV a suscité beaucoup d’intérêt en raison de sa présence universelle dans les verres. Cette anomalie, appelée “boson peak” (BP), apparaît comme un pic dans la VDOS réduite par rapport à la prévision du continuum élastique de Debye, dans une région d’énergies où le modèle de Debye fonctionne encore assez bien pour les correspondants cristaux. Dans ce travail de Thèse on présente les résultats d’une étude expérimentale de la dynamique vibrationnelle dans des verres du sorbitol et du soufre, par diffusion inélastique de la lumière, des rayons x et des neutrons. Dans le cas du sorbitol, ces résultats montrent clairement que le BP est lié à des anomalies observées dans la courbe de dispersion acoustique dans la région mésoscopique des vecteurs d’onde de quelques nm−1. En outre, l’étude de la dépendance en température de ces propriétés montre que cette connexion est maintenue même avec les changements de température. Enfin, le comportement des modes à haute fréquence peut être utilisé pour reproduire quantitativement la forme du BP, ce qui suggère une forte relation entre les propriétés acoustiques dans la région mésoscopique et le BP. Ce comportement semble être universel dans les verres. Dans le cas du soufre vitreux le BP est situé à l’extérieur de la fenêtre d’énergies qui peut être sondée par IXS et donc il n’est pas possible expérimentalement d’étudier le caractère des excitations collectives correspondantes
One of the most challenging issue in condensed matter physics concerns the understanding of the vibrational properties of glasses. In particular, an anomaly present in the vibrational density of states (VDOS) at energies of few meV has attracted much interest due to its universal occurrence in glasses. This anomaly, called ”boson peak” (BP), appears as a peak in the reduced VDOS over the Debye, elastic continuum prediction in an energy range where the Debye model still works reasonably well for the corresponding crystals. In this PhD work we present the results of an experimental study of the vibrational dynamics in glassy sorbitol and sulfur by means of inelastic scattering of light, x-ray and neutron. In the case of sorbitol, these results show that the boson peak is clearly related to anomalies observed in the acoustic dispersion curve in the mesoscopic wavenumber range of few nm−1. Moreover, the study of the temperature dependence of these properties shows that this connection is kept under temperature changes. Finally, the behavior of the high frequency modes can be used to quantitatively account for the BP, suggesting a strong connection between acoustic properties in the mesoscopic range and boson peak. This behavior seems to be universal in glasses. In the case of glassy sulfur the BP is located at energies outside the window which can be probed by IXS and it is not possible experimentally to investigate the character of the corresponding collective excitations

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42

Perkins, Thomas Edward James. "The effects of electronic quenching on the collision dynamics of OH(A) with Kr and Xe". Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:5998e249-35ff-4d05-9c13-9b65d59b11d9.

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This thesis presents an experimental and theoretical study of the collision dynamics of OH(A²Σ⁺) with Kr and Xe. These two systems both exhibit a significant degree of electronically non-adiabatic behaviour, and a particular emphasis of the work presented here is to characterise the competition and interplay between electronic quenching on the one hand, and electronically adiabatic collisional processes on the other. Quenching takes place close to the bottom of the deepest potential well for both systems. In collisions that remain in the excited electronic state, this same region of the potential is also largely responsible for rotational energy transfer (RET) and the collisional depolarisation of angular momentum. Therefore, the direct competition between these processes suppresses the cross-sections for RET and collisional depolarisation from their expected value in the absence of quenching. To investigate this, experiments were carried out to measure cross-sections for the collisional transfer of electronic, vibrational and rotational energy in OH(A, v=0,1) + Kr and OH(A, v=0) + Xe. In addition, measurements were made of the j-j' correlation -- that is, the relationship between the angular momentum of the OH radical before and after a collision -- in collisions with Kr and Xe, using the experimental technique of Zeeman quantum beat spectroscopy. Collisions with both Kr and Xe tend to effectively depolarise the angular momentum of the OH radical, due to the very anisotropic character of the potential on which the process occurs. Electronic quenching, which plays an essential role in both systems, is more prevalent with xenon as the crossing to the ground state potential is located in a more accessible location. These experimental results were compared with single surface quasi-classical trajectory (QCT) calculations, where the overestimate of rotational energy transfer or collisional depolarisation helps to elucidate the degree to which the presence of quenching suppresses these processes. Surface hopping QCT was then used to account for non-adiabatic transitions in the theory, which led to an improvement in agreement with experiment. However, standard surface hopping QCT theory failed to account for the full extent of quenching in these two systems. A major focus of this work is therefore on the development of an extension to standard surface hopping QCT theory to incorporate rovibronic couplings. In non-linear configurations, the excited state of the OH + Kr, Xe systems has A' symmetry, while the ground state is split into symmetric (A') and antisymmetric (A'') components. For these symmetry reasons, coupling is restricted to the two states of the same symmetry, however a rotation of the correct (A'') symmetry can induce transitions to the A'' state too. Inclusion of all three electronic states, and the relevant couplings between them, is found to be crucial for a proper description of experimental reality.

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Chefdeville, Simon. "Dynamique de collisions moléculaires à très basse énergie : mise en évidence expérimentale de résonances quantiques". Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0340/document.

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Les calculs théoriques prévoient que la dynamique d’excitation rotationnelle desmolécules CO et O2, induite par collision avec H2, est dominée par des résonancesquantiques aux très basses énergies. Leur mise en évidence expérimentale estrendue difficile par la nécessité d’obtenir des énergies de collision très faibles et unegrande résolution en énergie. Les expériences menées grâce à un montage defaisceaux moléculaires croisés à angle d’intersection variable, nous permettent ainsid’observer le seuil des transitions j = 0  1 de CO à 3,85 cm-1 et Nj = 10  11 de O2à 3,96 cm-1. Ces énergies correspondent à l’énergie cinétique moyenne d’un gaz àune température inférieure à 4 K. Les pics dans le tracé des sections efficacesintégrales en fonction de l’énergie de collision, constituent la première observationexpérimentale de résonances pour des processus inélastiques. Le bon accord avecles calculs théoriques permet de valider les potentiels d’interaction et ainsi dedéduire les constantes de vitesse pour la modélisation du milieu interstellaire. Nosrésultats expérimentaux mettent en relief la nature quantique des interactionsmoléculaires aux très basses énergies
Theoretical calculations predict that the dynamics of rotational excitation of CO or O2molecules, induced by collisions with H2, are dominated by quantum scatteringresonances at very low energies. However, experimental observation of these effectsis challenging: very low collision energies and high energy resolution are bothrequired. Experiments performed with a crossed molecular beam apparatus withvariable intersection angle allow us to observe the thresholds of the CO (j = 0  1)transition at 3.85 cm-1 and the O2 (Nj = 10  11) transition at 3.96 cm-1, whichcorrespond to the average kinetic energy of a gas below 4 K. The peaks in theintegral cross section’s collision energy dependence constitute the first experimentalobservation of resonances in an inelastic process. The good agreement betweentheory and experiment reinforces the confidence in the interaction potentials used todeduce rate coefficients for modeling the interstellar medium in the 1-20 K range. Ourexperimental results highlight the quantum nature of molecular interactions at verylow energies

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Valle, Orero Jessica. "Dynamics and thermal behaviour of films of oriented DNA fibres investigated using neutron scattering and calorimetry techniques". Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2012. http://tel.archives-ouvertes.fr/tel-00734670.

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The majority of structural studies on DNA have been carried out using fibre diffraction, while studies of its dynamics and thermal behaviour have been mainly performed in solution. When the DNA double helix is heated, it exhibits local separation of the two strands that grow in size with temperature and lead to their complete separation. This work has investigated various aspects of this phenomenon. The experiments reported in this thesis were carried out on films of oriented fibres of DNA prepared with the Wet Spinning Apparatus. Thus, sample preparation and characterisation are essential parts of the research. The structures of two forms of DNA, A and B, have been explored as a function of relative humidity at fixed ionic conditions. A method to eliminate traces of ever-present B-form contamination in A-form samples was established. The high orientation of the DNA molecules within the samples allowed us to investigate dynamical fluctuations and the melting transition of DNA using neutron scattering, which can provide the spatial information crucial to understand a phase transition, probing the static correlation length along the molecule as a function of temperature. The transition has been investigated for A and B-forms in order to understand its dependence on molecular configuration.Furthermore, after the first melting, denatured DNA films show typical glass behaviour. Their thermal relaxation has been explored using calorimetry.Neutron and X-ray inelastic scattering (INS and IXS) were used in the past to measure longitudinal phonons in fibre DNA, and the results shown disagreement. Recent INS measurements supported with phonon simulations have been crucial to understand the different dispersion curves reported to date. Experiments using INS and IXS have been carried out to continue with this investigation. Attempts to observe the transverse fluctuations associated to the thermal denaturing of DNA, never experimentally investigated before, have been made.

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45

McEniry, E. J. "Dynamical Simulation of Inelastic Quantum Conduction". Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527855.

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Sunthar, P. "Characterisation and Analysis of a Vibro-fluidised Granular Material". Thesis, Indian Institute of Science, 2001. https://etd.iisc.ac.in/handle/2005/249.

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The present work is concerned with the mathematical modelling of a bed of granular material in a gravitational field vertically fluidised by a vibrating surface. The particles are in rapid motion, and lose energy by inelastic collisions. The steady state is maintained by a balance of the rate of dissipation of energy in inelastic particle collisions and the rate of transfer of energy due to particle collisions with the vibrating surface. The limit where the energy dissipation due to inelastic collisions is small compared to the mean kinetic energy of the particles is considered. This non-equilibrium steady state is similar to a dilute gas at equilibrium with a uniform temperature and an exponentially decaying density, obtained from the ideal gas equation of state. From the analysis of this state, four non-dimensional numbers are derived which uniquely specify the state of the system. A perturbative analysis about the uniform temperature state is carried out and analytical solutions to the macroscopic variables of the system are obtained using two types of approximations. The first is a hydrodynamic model using constitutive relations from the general kinetic theory of granular media, and the second is a kinetic theory formulation derived exclusively for the vibro-fluidised bed. The latter permits an anisotropy between the horizontal and vertical directions due to the anisotropic nature of the source of energy at the bottom wall. The kinetic theory is extended to incorporate the corrections due to the high density effects, which is similar to the Enskog correction to dense gases. An event driven (ED), or hard sphere molecular dynamic (MD), simulation of the vibrated bed is carried out. The quantitative predictions of the theories are validated by the simulation. A systematic probing of the parameter space within the ED simulations revealed two new phenomena in a vibro-fluidised bed which are inhomogeneous in the horizontal direction. These are convection rolls similar to the Rayleigh-Benard instability in fluids, and a clustering instability leading to a phase separation. The instabilities are characterised using a phase diagram. The homogeneous states close to these new states are adequately described by the models developed here. An analysis of the stability of this state could have implications in understanding the instabilities in driven granular materials (such as in sheared media and fluidised beds) in general, and pattern formation in vibrated beds in particular.

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47

Sunthar, P. "Characterisation and Analysis of a Vibro-fluidised Granular Material". Thesis, Indian Institute of Science, 2001. http://hdl.handle.net/2005/249.

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Abstract (sommario):

The present work is concerned with the mathematical modelling of a bed of granular material in a gravitational field vertically fluidised by a vibrating surface. The particles are in rapid motion, and lose energy by inelastic collisions. The steady state is maintained by a balance of the rate of dissipation of energy in inelastic particle collisions and the rate of transfer of energy due to particle collisions with the vibrating surface. The limit where the energy dissipation due to inelastic collisions is small compared to the mean kinetic energy of the particles is considered. This non-equilibrium steady state is similar to a dilute gas at equilibrium with a uniform temperature and an exponentially decaying density, obtained from the ideal gas equation of state. From the analysis of this state, four non-dimensional numbers are derived which uniquely specify the state of the system. A perturbative analysis about the uniform temperature state is carried out and analytical solutions to the macroscopic variables of the system are obtained using two types of approximations. The first is a hydrodynamic model using constitutive relations from the general kinetic theory of granular media, and the second is a kinetic theory formulation derived exclusively for the vibro-fluidised bed. The latter permits an anisotropy between the horizontal and vertical directions due to the anisotropic nature of the source of energy at the bottom wall. The kinetic theory is extended to incorporate the corrections due to the high density effects, which is similar to the Enskog correction to dense gases. An event driven (ED), or hard sphere molecular dynamic (MD), simulation of the vibrated bed is carried out. The quantitative predictions of the theories are validated by the simulation. A systematic probing of the parameter space within the ED simulations revealed two new phenomena in a vibro-fluidised bed which are inhomogeneous in the horizontal direction. These are convection rolls similar to the Rayleigh-Benard instability in fluids, and a clustering instability leading to a phase separation. The instabilities are characterised using a phase diagram. The homogeneous states close to these new states are adequately described by the models developed here. An analysis of the stability of this state could have implications in understanding the instabilities in driven granular materials (such as in sheared media and fluidised beds) in general, and pattern formation in vibrated beds in particular.

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48

Li, Qingming. "Dynamic inelastic response and failure of structural elements". Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266315.

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The dynamic shear response and failure of structural elements under transverse impact loads are studied in the present work. The dynamic shear response is one of the important response modes in structural elements under transverse impact loads, which may lead to various shear failures depending on the loading rates and intensities. Transverse shear localization phenomena, which are represented by a shear hinge, have been observed in several structural elements when subjected to transverse dynamic loading and are studied in this thesis. The features of a stationary shear hinge are illustrated using a rigid, perfectly plastic simplification. The dimensions of a shear hinge for several structural elements are estimated both theoretically and numerically. It is shown that there exists a fixed shear hinge length for a given two-dimensional structural element. The length of a shear hinge is determined by its bending and shearing properties which can be obtained from a quasi-static analysis. When the shear hinge length has been determined, the conventional rigid-plastic method can be used to calculate the shear strain and shear strain rate within the shear hinge during the shear response phase. These theoretical results are employed to model Menkes and Opat' s beam problem to find two possible failure mechanisms, i.e., ductile shear failure and adiabatic shear failure and the associated transition conditions. A double-shear beam(DSB) subjected to a transverse projectile impact is studied experimentally and numerically in order to provide a more fundamental understanding on the features of structural failure in a localised shear zone. Both ductile tensile failure and adiabatic shear banding failure are found in the shear notch section. An analytical model and FEM simulation are developed to predict the DSB response and failures. The theoretical background of the strain energy density failure criterion is discussed and verified in this problem. Among the failure criteria examined in the current study, the strain energy density failure criterion is observed to give reasonable predictions for the failure initiation.

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49

Zhu, Ling. "Dynamic inelastic behaviour of ship plates in collision". Thesis, University of Glasgow, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324960.

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50

García, Vázquez Ricardo Manuel. "Étude théorique de la relaxation vibrationnelle de l’eau par collisions avec quelques uns des constituants les plus abondants des atmosphères des étoiles évoluées". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0441.

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L’existence de molécules d’eau dans l’espace a été confirmée en 1964 lorsque des raies du spectre de vapeur d’eau ont été détectées dans l’atmosphère d’étoiles riches en oxygène. Des raies de rotation ont depuis été détectées dans de très nombreux environnements, incluant les nuages moléculaires et les régions de formation stellaire. Les modèles astrophysiques utilisés pour modéliser les conditions physiques régnant dans ces milieux ne prennent pour l’instant en compte que la rotation des molécules d’eau. Mais, des études d’environnements plus chauds, comme les enveloppes et les atmosphères des étoiles évoluées, ont conduit plus récemment à la détection de molécules d’eau dans des états vibrationels excités. La détermination des taux de relaxation vibrationnelle de l’eau par collisions avec les éléments les plus abondants du milieu interstellaire, H2, He, H and e− est ainsi devenue nécessaire à la modélisation de ces environnements. Malheureusement, les données théoriques actuellement disponibles se limitent aux transitions rotationnelles. Les études expérimentales souffrent des mêmes limitations mais offrent la possibilité de valider les résultats des modèle théorique employés. Lorsque les systèmes astrophysiques pertinents sont trop difficiles à mesurer, les expérimentateurs étudient des systèmes modèles choisis pour leurs similarités. C’est pourquoi des études de relaxation rotationnelle ont été menées à la fois pour des systèmes d’intérêt astrophysique et pour des sytèmes modèles dont les résultats ont été comparés aux données expérimentales disponibles. C’est le cas des relaxations rotationelles de H2O, D2O et HDO par collisions avec le néon. Un excellent accord est obtenu avec les résultats d’une expérience récente pour les collisions HDO+ Ne validant ainsi la surface d’énergie potentielle (PES) développée pour ce système. Celle ci est utilisée pour déduire des règles de préférence pour les collisions de l’eau avec des gaz rares. La section efficace différentielle (DCS) offrant l’information la plus détaillée décrivant un processus collisionnel, les collisions H2O+Ne, Ar et Xe sont également étudiées, et un très bon accord est obtenu avec les résultats expérimentaux. Le deuxième objectif principal de ce travail est d’étudier la relaxation collisionnelle de niveaux vibrationellement excités de l’eau. La relaxation du bending de l’eau par collision avec l’argon et de D2O par collision avec l’hélium et l’argon sont les premiers systèmes étudiés à l’aide de la méthode Rigid Bender Close Coupling (RBCC). La comparaison avec l’experience a permis de valider cette approche. La dernière partie de ce manuscrit est consacrée à la relaxation vibrationelle de l’eau par collisions avec H2. La méthode RBCC est étendue pour inclure tous les modes vibrationnels de l’eau ainsi que pour traiter les collisions avec une molécule linéaire au lieu d’un atome. Un nouveau code, appelé "Divitas", est développé permettant d’effectuer à la fois des calculs Close Coupling (CC) et Coupled States (CS) pour étudier la relaxation rovibrationnelle de molécules triatomiques, telles que l’eau par collision avec des molécules linéaires, telles que H2. Ce nouveau code est d’abord utilisé pour étudier la relaxation du bending de l’eau par collisions avec H2 et un nouvel ensemble de taux Close Coupling incluant les transitions ro-vibrationnelles est produit. Le taux calculé est en excellent accord avec sa valeur expérimentale à 295 K. Néanmoins, le coût de calcul élevé de la méthode CC représente un obstacle important à l’étude de la relaxation d’états vibrationnels plus excités. Pour surmonter cette difficulté, l’utilisation de l’approximation CS est d’abord validée par comparaison avec les résultats CC. Elle est ensuite utilisée pour étudier la relaxation du deuxième état excité de bending en utilisant pour l’eau une base incluant ses cinq premiers états vibrationnels
The existence of water molecules in space was confirmed in 1964 when the presence of spectral lines of water vapour was detected in the atmosphere of O-rich stars. Subsequently, water has been identified as a prevalent molecule across the universe. Rotational lines have now been observed in a variety of environments, including molecular clouds and star-forming regions. For many years, the astrophysical models used to model the physical conditions prevailing in these environments have only considered the water molecule rotation. However, studies of warmer environments, such as the envelopes and atmospheres of evolved stars, have led to the detection of vibrationally excited H2O molecules. Also, vibrational de-excitation rate coefficients for the collisions of H2O with the most abundant elements in the interstellar media, including H2, He, H and e− are needed to model these environments. Unfortunately, most of the currently available theoretical collisional data are limited to rotational transitions. Experimental studies suffer from the same limitation but offer the opportunity to validate the accuracy of the theoretical model employed. Furthermore, when the relevant astrophysical systems are too challenging to measure, experimentalists often turn to similar systems as a proxy for the systems of interest. The present work, in addition to providing new vibrational data, then also includes rotational (de)excitation studies of systems which are compared with available experimental data. This is the case of the rotational (de)excitation of H2O, HDO and D2O molecules by collisions with Ne. An excellent agreement between theory and a new recent experiment is obtained for the collisions of HDO with Ne validating the new PES developed for this system, which was then used to infer collisional propensity rules for these collisions. Similarly, as the differential cross section (DCS) offers the most detailed information about a collisional process, the collisions of H2O with Ne, Ar and Xe are also studied, and a very good agreement is obtained with the experimental results. The second main objective of this work is to study the collisional relaxation of vibrationally excited levels of water. The first systems to be studied using the Rigid Bender Close Coupling method (RBCC) were the bending relaxation of H2O by collision with Ar and of D2O by collision with He and Ar atoms. The subsequent comparison with experimental data allowed validating this approach. The last part of this manuscript is dedicated to the vibrational relaxation of H2O by collisions with the most abundant astrophysical collider, H2. The RBCC method is extended to include all the vibrational modes of H2O and the collisions with a linear molecule instead of an atom. A new code, called "Divitas," is developed allowing to perform both close coupling (CC) and coupled states (CS) calculations to study the rovibrational relaxation of triatomic molecules, such as H2O, in collision with linear molecules, such as H2. The new code is first employed to investigate the bending relaxation of H2O by collisions with H2 utilising the CC method and a new set of rate coefficients including ro-vibrational transitions is produced. Our global bending relaxation rate is in excellent agreement with the experimental value reported at 295 K. Nevertheless, the high computational cost of the CC method represents a significant obstacle to the study of more excited vibrational states. To circumvent this difficulty, the use of the CS approximation is first validated by comparison with the CC results. It is then subsequently employed to investigate the relaxation of the first bending overtone utilising a H2O basis set incorporating the first five vibrational states of the water molecule

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Tesi sul tema "Inelastic dynamics"

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