Dissertations / Theses on the topic 'Quadrupolar phase'
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1
Sales, Nilva Lúcia Lombardi. "Interação quadrupolar em compostos cúbicos à base de praseodímeo." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-24062008-085924/.
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Este trabalho segue os passos históricos, descritos na literatura, das interações normalmente consideradas nos sistemas intermetálicos de terras raras. O capítulo 2 considera o efeito do campo elétrico gerado pela distribuição de cargas no cristal, por isso denominado de campo elétrico cristalino. Já o capítulo 3 descreve o passo seguinte que é considerar uma interação entre dois íons vizinhos do cristal. Essa interação ocorre por mediação de elétrons itinerantes e é conhecida como interação de Ruderman-Kittel- Kasuya-Yosida, ou interação RKKY. Considerando-se apenas estas duas interações já é possível explicar boa parte do comportamento magnético dos compostos intermetálicos de terras raras. O PrMg2 é uma exceção para o qual a interação quadrupolar tem sido sugerida na literatura. A adição desta interação é o principal objetivo deste trabalho e tema do capítulo 4. A dependência dos parâmetros de ordem magnético e quadrupolar com a temperatura são estudados com a aproximação de campo médio. A estabilidade destes parâmetros é analisada através da energia livre na aproximação de campo médio (ao contrário da expansão de Landau, uma aproximação comum na literatura). Um diagrama de fases é obtido mostrando natureza do estado fundamental do Hamiltoniano de campo médio e o tipo de transição de fase (primeira ou segunda ordem) em função dos acoplamentos magnéticos e quadrupolares. É mostrado que o PrMg2 tem uma transição de fase de segunda ordem, como observado experimentalmente, após a inclusão de um acoplamento antiferroquadrupolar do tipo Heisenberg. Os cálculos numéricos foram feitos usando o programa Maple 5, e os códigos usados são mostrados nos apêndices A e C.This work considers the presence of interactions in rare earth intermetallic compounds with cubic symmetry. In chapter 2 the crystalline electric field is taken into account and in chapter 3 an RKKY interaction between nearest neighbours is introduced in order to obtain magnetic order in the crystal. These interactions alone are sufficient to explain magnetic behavior of several based Pr compounds, with PrMg2 an exception for what a quadrupolar interaction has been proposed in the literature; the addition of this interaction constitutes the principal goal of this work and is developed in chapter 4. The temperature dependence of the magnetic- and quadrupolar-order parameters is studied under the mean-field approximation. The stability of those parameters are analyzed by means of an exact mean-field free energy (as opposed of a Landau expansion, an approximation common in the literature). A phase diagram is obtained relating the magnetic and quadrupolar couplings with the nature of the ground state mean-field Hamiltonian and the kind of the phase transitions (first or second). It is showed that the PrMg2 undergoes a second order phase transition, as observed experimentally, after an inclusion of a Heisenberg like antiferroquadrupolar coupling. The numerical calculations were performed using the Maple software and the codes are listed in the appendix.
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Bristow, Anthony Walter Thomas. "Laser desorption and high resolution studies in quadrupole ion trap mass spectrometry." Thesis, Nottingham Trent University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336973.
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Malik, A. Q. "Kinetic studies of gas phase cations by charge-exchange techniques in a two-quadrupole tandem mass spectrometer." Thesis, University of Essex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372588.
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Powoski, Robert A. "Molecular Structure Analyses of Asymmetric Hydrocarbon Liquid Compounds in the Gas Phase Using Chirped-pulse Fourier Transform Microwave Spectroscopy: Acyl Chlorides and Perfluorinated Acyl Chlorides." Thesis, University of North Texas, 2011. https://digital.library.unt.edu/ark:/67531/metadc103374/.
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Examinations of the effects of (a.) alkyl carbon chain length and (b.) perfluorination of acyl chlorides; propionyl chloride, butyryl chloride, valeroyl chloride, and perfluorinated acyl chlorides; perfluoropropionyl chloride and perfluorobutyryl chloride, are reported and compared using CP-FTMW spectroscopy. All of these molecules are already published in various journals except for valeroyl chloride. The chapters are organized by molecule alkyl chain length and include some background theory. Conformational stability, internal rotation, helicity, and ionic character of the C-Cl bond via the nuclear electric quadrupole coupling constant (χzz) are analyzed. Results show syn, syn-anti/syn-gauche, and syn-anti-anti/syn-gauche-anti stable conformations. Internal rotation was only seen in propionyl chloride. Helicity was not observed. (χzz) was observed to be inert to alkyl chain length, ~ 60 MHz and ~ 65 MHz for the nonfluorinated and fluorinated acyl chlorides. Partial fluorination and varying functional groups are recommended.
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Hall, Robin Gibson. "The development of a quinquaquadrupole mass spectrometer : the study of ion-molecule reactions in the gas phase using multiple quadrupole instruments." Thesis, University of St Andrews, 1991. http://hdl.handle.net/10023/15506.
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The field of quadrupole mass spectrometry has grown enormously since the early 1980's. The invention of the triple quadrupole mass spectrometer led to the development of tandem quadrupole mass spectrometers of many different configurations. A large number of tandem quadrupole mass spectrometers have also been developed by linking one or more quadrupole mass filters to a traditional magnetic or electric filter. The versatility of multiple quadrupole mass spectrometers along with their potential to rapidly produce a huge amount of data on a particular ion makes them ideal instruments for routine analytical analysis as well as for fundamental research The quinquaquadrupole mass spectrometer has been developed as an extension to the available multiple quadrupole systems. It offers the possibility to obtain even more data on the fragmentation of ions as well as enabling the study of novel ions to be carried out. The development of the quinquaquadrupole mass spectrometer forms the main part of this thesis. Also discussed are the reactions studied to evaluate the instrumental performance. The the ion molecule reactions of some halogen containing cations with saturated and unsaturated hydrocarbons performed on the triple quadrupole mass spectrometer are also discussed.
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Hall, Bradley John. "Development of solid phase microextraction (SPME) and matrix assisted laser desorption ionization (MALDI) with quadrupole ion trap mass spectrometry for analytical applications /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Perumal, Karthick. "Epitaxial growth of Ge-Sb-Te based phase change materials." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2013. http://dx.doi.org/10.18452/16815.
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Ge-Sb-Te basierte Phasenwechselmaterialen sind vielersprechende Kandidaten für die Anwendung in optischen und elektrischen nicht-flüchtigen Speicheranwendungen. Diese Materialien können mit Hilfe von elektrischen oder optischen Pulsen reversibel zwischen der kristallinen und amorphen Struktur geschaltet werden. Diese stukturellen Phasen zeigen einen großen Unterschied in ihren elektronischen Eigenschaften, der sich in einer starken Änderung der optischen Reflektivität und des elektrischen Widerstands zeigt.Diese Studie befasst sich mit epitaktischem Wachstum und Analyse der epitaktischen Schichten. Der erste Teil der Arbiet befasst sich mir dem epitaktischen Wachstum von GeTe. Dünne GeTe Schichten wurden auf Si(111) und Si(001) Substraten mit einer Gitterfehlanpassung von 10.8% präpariert. Auf beiden Substraten bildet sich in der GeTe Schicht die [111] Oberflächenfacette parallel zur Si(001) und Si(111) Oberfläche aus. Während des inertialen Wachstums findet eine Phasentransformation von amorph zu kristallin statt. Diese Phasentransformation wurde mittels azimuthaler in-situ Beugung hochenergetischer Elektronen sowie in-situ Röntgenbeugung unter streifendem Einfall untersucht. Der zweite Teil der Arbeit wird die Epitaxie sowie die strukturelle Charakterisierung dünner Sb2Te3 Schichten dargestellt. Der dritte Teil umfasst die Epitaxie terniärer Ge-Sb-Te Schichten . Zum Wachstum wurden sowohl die Substrattemperatur als auch die Ge, Sb und Te Flüsse variiert. Es wird gezeigt, dass die Komposition der Schicht stark von der Wachtumstemperatur abhängt und nur entlang der pseudibinären Verbindungslinie von GeTe-Sb2Te3 variiert. Zur Kontrolle des Wachstums wurde dabei die in-situ Quadrupol Massenspektroskopie verwendet. Es zeigen sich diverse inkommensurate Beugungsmaxima entlang der [111] Oberflächennormalen der Schichten, anhand derer die Ausbildung einer Lehrstellen Ordnung in Form einer Überstruktur diskutiert wird.Ge-Sb-Te based phase change materials are considered as a prime candidate for optical and electrical data storage applications. With the application of an optical or electrical pulse, they can be reversibly switched between amorphous and crystalline state, thereby exhibiting large optical and electrical contrast between the two phases, which are then stored as information in the form of binary digits. Single crystalline growth is interesting from both the academic and industrial perspective, as ordered Ge-Sb-Te based metamaterials are known to exhibit switching at reduced energies. The present study deals with the epitaxial growth and analysis of Ge-Sb-Te based thin films. The first part of the thesis deals with the epitaxial growth of GeTe. Thin films of GeTe were grown on highly mismatched Si(111) and (001) substrates. On both the substrate orientations the film grows along [111] direction with an amorphous-to-crystalline transition observed during the initial stages of growth. The amorphous-to-crystalline transition was studied in-vivo using azimuthal reflection high-energy electron diffraction scans and grazing incidence x-ray diffraction. In the second part of the thesis epitaxy and characterization of Sb2Te3 thin films are presented. The third part of the thesis deals with the epitaxy of ternary Ge-Sb-Te alloys. The composition of the films are shown to be highly dependent on growth temperatures and vary along the pseudobinary line from Sb2Te3 to GeTe with increase in growth temperatures. A line-of-sight quadrupole mass spectrometer was used to reliably control the GeSbTe growth temperature. Growth was performed at different Ge, Sb, Te fluxes to study the compositional variation of the films. Incommensurate peaks are observed along the [111] direction by x-ray diffraction. The possibility of superstructural vacancy ordering along the [111] direction is discussed.
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Robb, Damon Bradley. "Studies of the effects of the amplitude and phase of the RF potential on the trapping process in laser desorption quadrupole ion trap mass spectrometry." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ34617.pdf.
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Christides, Achille. "Spectrométrie pulsée de R. Q. N. Et contribution à l'étude de la phase incommensurable de β-ThBr ₄." Paris 11, 1987. http://www.theses.fr/1987PA112068.
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On décrit la réalisation d'un spectromètre pulsé informatisé effectuée à partir d'un montage antérieur dont les performances ont été améliorées. Cette réalisation se situe dans la perspective de l'extension des possibilités de recherche du service de R. Q. N. Et s'intègre dans un ensemble informatisé assurant le traitement des données expérimentales et une automatisation des mesures. Le spectromètre réalisé est entièrement transistorisé et couvre une gamme de fréquences s'étendant de quelques centaines de kilohertz à 60 MHz. Les circuits sont à large bande à l'exception d'un circuit accordable réducteur de bande passante destiné à éviter la saturation du récepteur par le bruit aux gains élevés et du Circuit Oscillant principal. Il en résulte à ce niveau une réduction du nombre des réglages nécessaires et une simplification dans l'utilisation de l'ensemble. Les progrès réalisés concernent le taux de réjection de la porte analogique (> 60 db jusqu'à 80 MHz)- l'augmentation de la fréquence maximale de fonctionnement (80 MHz pour la porte et le récepteur, 60 MHz pour l'émetteur)- la puissance d'émission (100 W) et le temps de récupération du récepteur (15 µs en l'absence du Circuit Oscillant contenant l'échantillon. Ce spectromètre a été utilisé pour l'étude de la phase incommensurable de ThB4. Les études antérieures sur ce produit avaient été effectuées avec un spectromètre à superréaction dont les limitations pour l'étude de la forme des raies sont connues. Avec le spectromètre pulsé la nature de la raie de résonance large fournie par l'échantillon dans la phase incommensurable a été confirmée; dans la gamme de température étudiée dans ce travail (77-95K), la raie reste sensiblement symétrique (indiquant une modulation sinusoïdale simple de la structure cristalline). L'étude de T1 montre la forte relaxation nucléaire au voisinage de la transition de phase en relation avec les fluctuations associées à la condensation du "mode mou" responsable de la transitionWe describe the realization of the radio-frequency sections of a pulsed and computerized N. Q. R. Spectrometer, the design of which is derived from a system existing at the Laboratory. The performances were improved and the design made with a view to increase the versatility of the N. Q. R. Research Group facilities. The all solid-state spectrometer can be operated from a few hundred hertz up to 60 MHz. Circuits are wide-band except for the tank circuit and a tunable pass-band circuit provided to reduce the amplified noise level; as a result adjustments when operating the system are minimized and phase shift problems are eliminated. The rejection ratio of the analogic gate is increased and still 60 db at 80 MHz. The transmitting power stage, also transistorized, can deliver one hundred watts up to 60 MHz time 15 µs. The receiver pass-band is 80 MHz and its recovery when the high-Q tank circuit is not connected. The spectrometer has been used for investigating the incommensurate phase of ß-ThBr4 below 96 K. As compared with previous measurements made with a SRO spectrometer of poor re solution as line shape studies are considered, this series of investigations brings new pieces of information about the actual shape of the broad bromine N. Q. R. Line observed in the incommensurate phase below 96 K. In the range of temperature investigated so far (77-96 K), the line remains quite symmetrical with respect to its center frequency suggesting that the modulation is of the sine plane wave type. Investigation of the relaxation time, T1, shows a strong relaxation near the phase transition temperature quite probably related to the soft mode condensation at the transition temperature
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Bonnisseau, Dominique. "Etude des structures magnétiques de composés de neptunium (NpAs, NpSb, NpSe et NpRu2Si2)." Grenoble 1, 1987. http://www.theses.fr/1987GRE10144.
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Merloti, Karina. "Condensat de Bose-Einstein dans un piège habillé : modes collectifs d'un superfluide en dimension deux." Phd thesis, Université Paris-Nord - Paris XIII, 2013. http://tel.archives-ouvertes.fr/tel-00949914.
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Cette thèse présente la production d'un gaz dégénéré de rubidium 87 dans le régime quasi bidimensionnel (2D) et l'étude des modes collectifs de ce gaz. Nous montrons que le gaz quasi-2D peut être amené en dessous du seuil de la transition Berezinskii-Kosterlitz-Thouless. Nous montrons le caractère superfluide du gaz dégénéré par la présence des modes quadrupolaire et ciseaux, dont nous mesurons les fréquences d'oscillation. Son caractère bidimensionnel est vérifié par la mesure de la fréquence du mode monopolaire. Nous mettons en évidence l'influence du confinement transverse et de la troisième dimension sur la fréquence de ce mode. Pour produire le superfluide, un condensat de Bose-Einstein est d'abord produit dans un piège quadrupolaire bouché par un faisceau laser très désaccordé et soigneusement optimisé pour réduire les pertes Majorana par renversement de spin. Le condensat est ensuite transféré vers un "piège habillé", c'est-à-dire un potentiel adiabatique dans lequel les atomes sont habillés par un champ radiofréquence. Pour rendre le piège plus anisotrope, le gradient magnétique est augmenté au maximum, ce qui nous permet d'explorer le régime quasi-2D pour le gaz de Bose. Les deux types de piège utilisés sont caractérisés en détail. Nous tirons parti de la souplesse du potentiel adiabatique pour exciter et étudier les modes collectifs.
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Labouze, Xavier. "Etude par résonances nucléaires des propriétés magnétiques des cuprates supraconducteurs dans leurs phases isolantes." Grenoble 1, 1994. http://www.theses.fr/1994GRE10042.
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Cette these porte sur l'etude des proprietes magnetiques des cuprates supraconducteurs dans leurs phases isolantes. Les techniques experimentales utilisees sont la resonance nucleaire, magnetique (rmn) et quadrupolaire (rqn). La premiere partie presente une revue des proprietes essentielles des cuprates supraconducteurs. La deuxieme explique particulierement comment utiliser la rqn. L'etude des composes au plomb type ybco (partie iii) montre que le magnetisme des cuprates doit etre quasi-2d quasi-heisenberg. La partie iv traite des composes ybco substitues au calcium. L'etude statique par mesures de largeurs de raie rqn a permis de determiner les temperatures de transition des composes intermediaires. Un modele de l'influence des porteurs de charges a ete construit. Une etude dynamique par mesures du temps de relaxation spin/reseau a aussi ete menee. On compare ces resultats avec ceux des composes monoplans lsco
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Manallah, Bouzid. "Observation de raies nouvelles dans le spectre de RQN de l'azote-14 dans quelques dérivés de la S-triazine et double résonance différée de l'azote dans la S-triazine à 4,2 k. : observation de la phase incommensurable de ThBr₄ à 4,2 K par RQN du brome." Paris 11, 1986. http://www.theses.fr/1986PA112021.
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Après avoir rappelé la théorie de la RQN et les facteurs qui l'influencent, on présente les spectromètres utilisés pour l'étude des résonances de l'azote-14 et du brome à 4,2 K. Une expérience de double résonance différée dans la s-triazine où les temps de relaxation sont longs, a permis d'apparier les raies ѵ+ et ѵ- ; elle a aussi permis de mettre en évidence des signaux d'émission avec les raies ѵ-. Dans le chlorure de cyanuryle, le spectre de RQN à 4,2 K a été complété par l'observation de deux raies nouvelles et dans la mélamine, neuf raies nouvelles ont été observées à cette température. Dans ThBr₄ , l'étude de la RQN du brome a pu être faite à 4,2 Ken utilisant une ligne demi-onde reliant la bobine r. F. Située dans le cryostat au spectromètre de superréaction ; nous avons ainsi pu observer, à cette température, la phase incommensurable déjà connue à température plus élevéeAfter a review of the theory of NQR and of factors that relate to it, the various kinds of spectrometers used to study Nitrogen-14 and Bromine NQR at 4. 2 K are described. A delayed double resonance experiment in s-triazine, where the relaxation times are long, allowed the ѵ+ and ѵ- in this substance lines to be paired. It was also possible to observe emission signals at the ѵ- lines. Complete NQR spectra of Cyanuric chloride and melamine were obtained by the observation of two new lines and nine new lines, respectively, at 4. 2 K. A Bromine NQR study of ThBr₄ was carried out at 4. 2 K by the use of a half-wavelength transmission line connecting the r. F. Coil in the cryostat to the superregenerative spectrometer. Thus, we were able to observe at this temperature the incommensurate phase which was already known to exist at higher temperature
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Halvachizadeh, Jaleh. "The Investigation of Reactions of Atomic Metal Anions with Small Hydrocarbons and Alcohols in the Gas Phase." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30646.
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Hydrocarbons are an abundant resource of carbon and hydrogen. For example, fossil can be used to produce useful organic compounds. However hydrocarbons seem to be inert. Thus, the activation of the C-H bond is a popular research area. Metals play the main role in most catalysts that convert hydrocarbons to starting materials in industry. The study of metals is important because the properties of the metal core greatly influences the reactivity of a catalyst.1
The study of the chemistry of metals in the gas phase provides valuable information about the properties of metals. This information can be expanded to the chemistry of metals in the condensed phase. Furthermore, it is often both more accurate and more manageable to study the profile of a reaction in the gas phase than in the condensed phase.2,3
There are many studies about metal cations in the gas phase due to ease of their production. However metals have low electronegativity, limiting the study of gas phase metal anions. Recently, a simple and efficient method to generate atomic metal anions was developed at the University of Ottawa in Dr. Mayer's research laboratory.4-6 Atomic metal anions of Fe-, Co-, Cu-, Ag-, Cs- and K- were generated in an electrospray ionization (ESI) source of a mass spectrometer (MS).
In this thesis study generated metal anions were reacted with small hydrocarbons of pentane, 1-pentene, 2-pentene and 1-pentyne to investigate the role of different metal anions in the activation of the C-H bond. Also metal anions were reacted with small alcohols of 1-butanol, 2-butanol and 2-methyl-2-propanol to compare the results.
Metal anions showed a variety of reactions with these hydrocarbons and alcohols. Fe- was the only metal anion to show the electron transfer reaction, indicating that alcohols are more electronegative than Fe- and less electronegative than other metal anions. Fe-, Co- and Ag- showed the complex formation reaction. All metal anions showed the deprotonation reaction. A deprotonation reaction follows the harpoon mechanism, the long range proton abstraction7, and depends on the gas phase acidity of fragments. The most informative reaction observed was the dehydrogenation reaction because a metal-containing fragment is observed as a product in the spectrum of this reaction. The observation of a metal-containing fragment in the spectrum is significant because it emphasizes the important role that metal anions play in this reaction. This suggests that a dehydrogenation reaction involves metal insertion into a C-H bond. Among the transition metal anions, it was observed that Fe- and Cu- are more reactive than Co- and Ag- with regards to the dehydrogenation reaction, probably because Fe- and Cu- have a greater hydrogen affinity than Co- and Ag- that facilitates the hydrogen abstraction reaction. Another reason could be that Fe- and Cu- have a greater gas phase acidity that leads to a more stable intermediate in the course of the reaction. The results of this thesis study revealed that Cs- and K- could not abstract H from these substrates, probably due to the absence of occupied d orbitals that would facilitate insertion into a C-H bond.
Some metal anions not only can insert into a C-H bond of alcohols but also can insert into a C-O bond of alcohols to form metal hydroxide anions. Alcohols are more reactive than hydrocarbons with regards to reactions with metal anions because they contain a functional group.
This thesis study shows that some atomic metal anions are able to activate the C-H bond and abstract two hydrogens to form a double bond in hydrocarbons. It is probable that the electronic configuration, gas phase acidity and hydrogen affinity of the metal anions governs their reactivity.
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Butson, Jeffery M. "Electron Transfer and Other Reactions Using Atomic Metal Anions." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30561.
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The atomic metal anions Rb-, Cs-, Cu-, Ag- and Fe- have been generated in the gas phase and reacted with various neutral reactants in a triple quadrupole mass spectrometer. The metal anions were formed via electrospray ionization of the metal-oxalate solutions and form in gas phase between the capillary and the first quadrupole. Neutral gas phase reactants investigated include NO, NO2, SO2, C6F5OH, C6F5NH2, C6F6, E-octafluoro-butene and 1,2,3/1,2,4/1,3,5 trifluoro-benzene. When possible, CBS-4M methods were used to suggest the lowest energy products based on relative energy. Observed reactions of atomic metal anions with the aforementioned neutral species include electron transfer and dissociative electron transfer to the neutral gas phase reactants. In addition, hydrogen abstraction and fluorine abstraction forming a neutral metal hydride or fluoride as well as the formation of multiply substituted metal-oxide/fluoride anions was also observed. Metal-complex anions observed from the gas phase reactions include CuF-,CuF2-,CuO-,CuO2-, FeO-, FeO2-, FeO3-, FeF-, FeF2-, FeF3-, CsF- and CsF2-.
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Chen, Shyh-Tzer, and 陳世澤. "Phase Transition of Clock Model with Dipolar and Quadrupolar Interactions." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/32482108431873078203.
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Das, Sambunath. "Quantum Phases and Magnetization Plateaus of Skewed Spin Ladders." Thesis, 2021. https://etd.iisc.ac.in/handle/2005/5702.
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This thesis deals with theoretical studies of skewed spin ladders which are two legged ladder with periodic slanted rung bonds and can be viewed as periodic fused rings with two different number of vertices. The spin at the vertices (sites) considered in this thesis are either spin ½ or 1. The skewed ladder is named an n/m ladder when the fused adjacent rings are with n and m vertices. These are quasi one-dimensional systems. The systems are studied by varying the rung exchange $J_1$, keeping the nearest neighbor leg exchange $J_2$ fixed at unity. The first chapter gives a brief historical introduction and discusses the origin of exchange interactions in materials. The spin-1/2 and spin-1 chains and quantum phases of the frustrated and dimerized spin-1/2 chains as well as the qualitative distinction between spin-1/2 and spin-1 antiferromagnetic Heisenberg chains are discussed. For investigating the skewed ladder systems, computational methods such as exact diagonalization technique in valence bond (VB) and constant Ms basis is described in chapter 2. For studying the large systems closer to the thermodynamic limit, the density matrix renormalization group (DMRG) method is introduced. Both finite and infinite DMRG algorithms are discussed and their implementation are outlined.
Chapter three presents the quantum phases in a 5/7 spin-1 skewed ladder system, studied numerically using the exact diagonalization technique up to 16 spins and the density matrix renormalization group method for larger system sizes. The study of diverse gs properties such as spin gap, spin-spin correlations, spin density, and bond order reveals that the system has four distinct phases, namely, the AF phase at small $J_1$; the ferrimagnetic phase with gs spin $S_G = n$ for $1.44 < J_1 < 4.74$ and with $S_G = 2n$ for $J_1 > 5.63$, where n is the number of unit cells; and a reentrant nonmagnetic phase at $4.74 < J_1 < 5.44$. The system also shows the presence of spin current at specific $J_1$ values due to simultaneous breaking of both reflection and spin parity symmetries. Quantum phase transitions of spin-1 3/4 and 3/5 skewed ladders are reported in chapter four. The ground state (gs) of the 3/4 ladder switches from a singlet to a magnetic state for $J_1 ≥ 1.82$. The gs of of the 3/5 skewed ladder is highly frustrated and has spiral spin arrangements and switches between singlet state and low spin magnetic states multiple times on tuning $J_1$ in a finite size system. The switching pattern is non-monotonic as a function of $J_1$, and depends on the system size. The 3/5 system also exhibits spontaneous spin parity and mirror symmetry breaking giving rise to spin current in the gs.
Magnetization plateaus, which are some of the most striking manifestations of frustration in low-dimensional spin systems, are observed in the spin-1/2, 5/7 skewed ladder. This system exhibits three significant plateaus at m = 1/4, 1/2 and 3/4, consistent with the Oshikawa-Yamanaka-Affleck condition. Our numerical as well as perturbative analysis shows that the ground state can be approximated by three weakly coupled singlet dimers and two free spins, in the absence of a magnetic field. With increasing applied magnetic field, the dimers progressively become triplets with large energy gaps to excited states, giving rise to stable magnetization plateaus. The cusps at the ends of a plateau follow the algebraic square-root dependence on the magnetic field strength. Magnetization plateaus in the spin- 1/2 model are observed at m = 1/3, 2/3 and 1 for 3/4 skewed ladder, m = 1/4, 1/2, 3/4 and 1 for 3/5 skewed ladder, and m = 0, 1/3, 2/3 and 1 for 5/5 skewed ladder. The occurrence of the m = 0 plateau in the 5/5 ladder implies a finite gap between the lowest energy levels in the singlet and triplet sectors. In the case of 3/4 and 5/5 ladders, quadrupolar phases were observed below the 1/3rd plateau, due to the binding of two magnons. These studies form the contents of chapters five and six. The last chapter of the thesis deals with investigation of the quantum phase transitions of the skewed ladders using entanglement and fidelity analysis. All the calculations are based on the exact diagonalization technique for finite system size. At the transition points, the entanglement entropy exhibits a discontinuous change, while fidelity shows a sharp dip. The transition points are accurately determined from the characteristics changes in entanglement entropy and fidelity.
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Yuan-po, Tai, and 戴元柏. "Gas-phase Host-Guest Chemistry in a Triple Stage Quadrupole Mass Spectrometry." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/29067586500586615028.
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碩士東海大學
化學系
87
The mass spectra of nitrogen-oxygen crown ethers and all nitrogen crown ethers have two major signals, [M+H]+and[2M+H]+. For these crown ethers, as the size of the macrocycle is larger, the steric barrier effect is greater, and it is difficult to form dimer complex. From collisionally activated dissociation (CAD) mass spectra of [M+H]+, we can find a series of losses of (C2H4O)n, (C2H5N)n, (C3H7N)n and some other fragments. The protonated dimer complex [2M+H]+ dissociates by loss of a monomer [M] without any other cleavage of the crown ether skeleton. The complex formation of nitrogen-oxygen crown ether with alkali metal has two tendencies. First, as the radius of metal ion greater, the form of complex ion fewer. Second, as the macrocycle of crown ether greater, the form of complex ion more. We conclude that it will induce the greater steric barrier by increasing the number of carbonic atom, and it is hard to form complex compound with the larger metallic ion clusters. In concert, it will have the same result by increasing the number of nitrogen atom of the crown ether. A special peak , [M+H]+, emerges from the CAD of [2M+H]+ forming with all nitrogen crown ether and alkali metal. It is to consider that all nitrogen crown ether has a greater proton affinity, so that it can catch a proton from the other crown ether on the dimer. Transition metal FeCl2, CoCl2, and NiCl2 can form [M+ACl]+ and [M-H+A]+ complexes with nitrogen-oxygen crown ether and all nitrogen crown ether, but CuCl2 can form these complexes with all nitrogen crown ether only. The reason may be the model of hard and soft acid and base. Additionally, the [M+ACl]+ complex dissociates by loss of HCl, giving [M+-H+A]+ fragment ion.
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Li, Geng. "The effective temperatures of gas-phase biological molecules stored in a quadrupole ion trap." 2008. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=771991&T=F.
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Santos, David Jorge Pires dos. "Identification of metabolites by liquid chromatography quadrupole time-of-flight mass spectrometric technique." Master's thesis, 2016. http://hdl.handle.net/10451/34605.
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Trabalho Final de Mestrado Integrado, Ciências Farmacêuticas, Universidade de Lisboa, Faculdade de Farmácia, 2016Analytical methods based on mass spectrometry and coupled to a chromatographic separation technique such as HPLC or GC, are crucial for investigating human metabolome, UPLC coupled with ESI-MS is a recent methodology representing an effective tool to separate and analyze molecules. The mains focus of this experimental work was to elucidate the influence of HILIC and Reversed-Phase chromatography on the analysis of compounds through ESI-MS. One additional aim was also to collect the identification data of selected compounds on a database for the building of a metabolomics library. This tool would allow to establish a match with results of subsequent analyses, minimizing the time spent on the identification of future analytes. Herein a UHPLC–MS method was applied for the first time to detect and identify a series of human metabolites and compounds found naturally on the human body. The procedures and molecules subjected to analysis are based on the protocol “Mass Spectrometry Metabolite Library of Standards”, commercially available by IROA Technologies. The kit contains a set of 619 standards. This work covers the first 253 compounds of the list. The analysis of compounds previously prepared as mixtures consisted on the chromatographic separation by HILIC or RP followed by positive or negative ESI-MS/MS. All the compounds were analyzed by the four possible combinations (HILIC, positive ESI; HILIC, negative ESI; RP, positive ESI; RP, negative ESI) as mixes of 12 standards distributed by four vials, one for each type of analysis. The results obtained were compiled and it was possible to conclude that HILIC is suitable to polar analytes whereas RP is preferable to non-polar compounds. Relatively to ESI, the positive ionization mode is applied with advantage to compounds that are able to accept a proton. Conversely, negative ESI is more effective to molecules which contain functional groups that readily lose a proton. Zwitterionic molecules are suitable to be analyzed by both modes. Some examples and exceptions to these general statements are presented.
Os métodos analíticos baseados em espectrometria de massa e acoplados a uma técnica de separação cromatográfica como HPLC ou GC, são cruciais para investigar o metaboloma humano. A análise por UPLC acoplada a ESI-MS é uma metodologia recente que representa uma ferramenta eficaz para separar e analisar moléculas. O foco principal deste trabalho experimental foi elucidar a influência de HILIC e cromatografia em fase reversa na análise de compostos através de ESI-MS. Um objectivo adicional foi também recolher os dados de identificação de compostos seleccionados numa base de dados para a construção de uma biblioteca de metabolitos. Esta ferramenta permitiria estabelecer uma correspondência com resultados de análises subsequentes, minimizando o tempo gasto na identificação de futuros analitos. Neste projecto, o método de análise por UHPLC-MS foi aplicado pela primeira vez para detectar e identificar uma série de metabolitos humanos e compostos encontrados naturalmente no corpo humano. Os procedimentos e moléculas submetidos à análise são baseados no protocolo "Mass spectrometry Metabolite Library of Standards", comercialmente disponível pela IROA Technologies. O kit contém um conjunto de 619 padrões. Este trabalho abrange os primeiros 253 compostos da lista. A análise de compostos previamente preparados em misturas consistiu na separação cromatográfica por HILIC ou RP seguida por ESI-MS/MS positiva ou negativa. Todos os compostos foram analisados pelas quatro combinações possíveis (HILIC, ESI positivo/ HILIC, ESI negativo/ RP, ESI positivo/ RP, ESI negativo) como misturas de 12 padrões distribuídos por quatro frascos, um para cada tipo de análise. Os resultados obtidos foram compilados e foi possível concluir que a separação por HILIC é adequada para analitos polares, enquanto que por RP é preferível para compostos não polares. Relativamente à ionização por ESI, o modo de ionização positiva melhor aplicado a compostos capazes de aceitar um protão. Por outro lado, a ESI negativa é mais eficaz para moléculas que contêm grupos funcionais que facilmente perdem um protão. As moléculas zwitteriónicas são passíveis de ser analisadas por ambos os modos. Alguns exemplos e excepções a estas ideias gerais são apresentadas.
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Monteleone, Marcello, Antonio Tagarelli, Bartolo Gabriele, and Roberto Bartolino. "Development and optimization by experimental design of solid phase microextraction gas chromatography triple quadrupole mass spectrometry methods in aqueous matrices." Thesis, 2012. http://hdl.handle.net/10955/1145.
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Dottorato di Ricerca in Organic Materials of Pharmacological Interest, Ciclo XXV, a.a. 2011-2012Il presente lavoro di tesi relativo all‘attività di ricerca svolta durante il triennio di dottorato ha riguardato la messa a punto di metodi analitici per la determinazione di analiti in due distinte aree di interesse. La prima di ambito clinico ed ha riguardato la quantificazione in urina di metaboliti riconosciuti come marker in diagnostica clinica. In particolare ci si occupati della sarcosina come biomarker del tumore alla prostata, e di tre acidi: acido omovanillico (HVA), acido vanilmandelico (VMA) ed acido 5-idrossindoloacetico (5-HIAA) come marker urinari del neuroblastoma. Il secondo ambito di lavoro ha riguardato la quantificazione di inquinanti in matrici acquose, vale a dire carbammati ed acidi perfluoroalchilici. In particolare gli analiti, previa derivatizzazione con alchilcloroformiati (eccetto i carbammati), sono stati estratti dalle matrici acquose (acqua e urina) tramite la tecnica della microestrazione in fase solida (SPME) e successivamente analizzati mediante un gascromatografo con analizzatore di massa a triplo quadrupolo (GC-QqQ-MS). Le variabili significative della microestrazione in fase solida in ciascun metodo sono state ottimizzate tramite l‘approccio multivariato dell‘ ― Experimental Design‖. L‘utilizzo della tecnica SPME ha consentito di poter estrarre gli analiti direttamente dal campione da analizzare minimizzando i tempi di preparazione dello stesso e riducendo l‘uso di solventi organici, ottenendo metodi poco costosi e basso impatto ambientale. L‘utilizzo dello spettrometro di massa triplo quadrupolo, ha consentito di raggiungere livelli di sensibilità molto elevati e, nel contempo, di identificare gli analiti con maggiore sicurezza. In tutti i metodi sviluppati, sono stati ottenuti ottimi risultati in termini di linearità accuratezza e precisione. Anche i valori dei limiti di rilevabilità (LOD) e dei limiti di quantificazione (LOQ) ottenuti in ciascun metodo possono essere considerati soddisfacenti.
Università degli Studi della Calabria
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Sagoo, Sandeep K. "Intrinsic Properties of Rhodamine B and Fluorescein Gas-phase Ions Studied using Laser-Induced Fluorescence and Photodissociation in a Quadrupole Ion Trap Mass Spectrometer." Thesis, 2011. http://hdl.handle.net/1807/29611.
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Studying the intrinsic properties of molecules in the gas-phase is advantageous, since it reduces the complexity present in solution that arises from interactions between the molecule of interest and other species present in the local environment, including those with the solvent itself.
In this report, the photophysical properties of gaseous cationic rhodamine B (RBH+) were determined and photodissociation reaction kinetics and power dependence of three prototropic forms of fluorescein; the cation ([F + H]+), monoanion ([F - H]-), and dianion ([F – 2H]-2), each of which possesses their own distinct spectral properties, were measured. The analyte ions of interest were formed via electrospray ionization, mass-selected and stored in a quadrupole ion trap mass spectrometer which has been customized to enable gas-phase spectroscopic studies.
Knowledge of the intrinsic photophysical properties of such chromophores in the gas-phase will enable a better understanding of how the local environment of the molecule alters its properties.
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Eliades, John Alexander. "A Radio Frequency Quadrupole Instrument for use with Accelerator Mass Spectrometry: Application to Low Kinetic Energy Reactive Isobar Suppression and Gas–phase Anion Reaction Studies." Thesis, 2012. http://hdl.handle.net/1807/32706.
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A radio frequency (rf) quadrupole instrument, currently known as an Isobar Separator for Anions (ISA), has been integrated into an Accelerator Mass Spectrometry (AMS) system to facilitate anion–gas reactions before the tandem accelerator. An AMS Cs+ sputter source provided > 15 keV ions that were decelerated in the prototype ISA to < 20 eV for reaction in a single collision cell and re-accelerated for AMS analysis. Reaction based isobar suppression capabilities were assessed for smaller AMS systems and a new technique for gas–phase reaction studies was developed.
Isobar suppression of 36S– and 12C3– for 36Cl analysis, and YF3– and ZrF3– for 90Sr analysis were studied in NO2 with deceleration to < 12 eV. Observed attenuation cross sections, σ [x 10^–15 cm^2], were σ(S– + NO2) = 6.6, σ(C3– + NO2) = 4.2, σ(YF3– + NO2) = 7.6, σ(ZrF3– + NO2) = 19. With 8 mTorr NO2, relative attenuations of S–/Cl– ~ 10^–6, C3–/Cl– ~ 10^–7, YF3–/SrF3– ~ 5 x 10^–5 and ZrF3–/SrF3– ~ 4 x 10^–6 were observed with Cl– ~ 30% and SrF3– > 90% transmission. Current isobar attenuation limits with < 1.75 MV accelerator terminal voltage and ppm impurity levels were calculated to be 36S–/Cl– ~ 4 x 10^–16, 12C3–/Cl– ~ 1.2 x 10^–16, 90YF3–/SrF3– ~ 10^–15 and 90ZrF3–/SrF3– ~ 10^–16.
Using 1.75 MV, four 36Cl reference standards in the range 4 x 10^–13 < 36Cl/Cl < 4 x 10^–11 were analyzed with 8 mTorr NO2. The measured 36Cl/Cl ratios plotted very well against the accepted values. A sample impurity content S/Cl < 6 x 10^–5 was measured and a background level of 36S–/Cl < 9 x 10^–15 was determined.
Useful currents of a wide variety of anions are produced in AMS sputter sources and molecules can be identified relatively unambiguously by stripping fragments from tandem accelerators. Reactions involving YF3–, ZrF3–, S– and SO– + NO2 in the ISA analyzed by AMS are described, and some interesting reactants are identified.
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Gardner, Myles Winston. "Development of chromogenic cross-linkers and selective gas-phase dissociation methods to assess protein macromolecular structures by mass spectrometry." Thesis, 2009. http://hdl.handle.net/2152/ETD-UT-2009-12-513.
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Selective gas-phase dissociation strategies have been developed for the characterization of cross-linked peptides and proteins in quadrupole ion trap mass spectrometers. An infrared chromogenic cross-linker (IRCX) containing a phosphotriester afforded rapid differentiation of cross-linked peptides from unmodified ones in proteolytic digests of cross-linked proteins by selective infrared multiphoton dissociation (IRMPD). Only the cross-linked peptides containing the chromogenic phosphate underwent IRMPD and unmodified peptides were not affected by IR irradiation. IRMPD of IRCX-cross-linked peptides yielded uncross-linked y-ion sequence tags of the constituent peptides due to secondary dissociation of all primary product ions which contained the chromophore, thus allowing successful de novo sequencing of the cross-linked peptides.
Peptides cross-linked via a two-step conjugation strategy through the formation of a bis-arylhydrazone (BAH) bond were selectively dissociated by ultraviolet radiation at 355 nm. The BAH-cross-linked peptides could be distinguished from not only unmodified peptides but also dead-end modified peptides based on the selectivity of ultraviolet photodissociation. In a complementary approach, electron transfer dissociation of BAH-cross-linked peptides resulted in preferential cleavage of the hydrazone bond which produced two modified peptides. These modified peptides were subsequently interrogated by CID which allowed for the original site of cross-linking to be pinpointed.
IRMPD was implemented in a dual pressure linear ion trap to demonstrate successful photodissociation of peptides having modest absorptivities. Peptides were observed to efficiently dissociation by IR irradiation exclusively in the low pressure cell whereas no dissociation was observed in the high pressure cell due to extensive collisional cooling. IRMPD provided greater sequence coverage of the peptides than CID and yielded product ion mass spectra which were predominantly composed of singly charged product ions which simplified spectral interpretation. IRMPD was further applied for the sequencing of small-interfering RNA. Complete sequence coverage was obtained and the results were compared to CID.text