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Laboratorní studium polní iontové emise z prachových zrn / Laboratory Study of Field Ion Emission from Dust GrainJeřáb, Martin January 2011 (has links)
Title: Laboratory study of field ion emission from dust grains Author: Martin Jeřáb Department: Department of Surface and Plasma Science Supervisor: Prof. RNDr. Jana Šafránková, DrSc., KFPP Abstract: Dust particles are common objects in space environment. As a dust particles, we call objects with typical sizes of several atoms up to approximately 100 µm. However, a total mass of dust particles is only about 1% of total mass of our galaxy, the presence of dust particles significantly affects environment. The most interesting is dynamics of dust particles and attached dust charging processes. The presented thesis consists of two main parts. The first part deals with the experimental study of field ion emission. Our measurements have been performed using gold and carbon spherical dust grains. It has been found that during the charging of dust particle using ion gun are the primary ions implanted under the surface of the dust particle from where they are release in the form of neutral gas. This releasing of implanted ions affects field ion emission for several hours. The second part of the thesis describes a development of new experimental apparatus determined to the study of photoemission dust charging and con- sequently to the "true" field ion emission study. Keywords: dust, dusty plasmas, charging properties, field...
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Politique économique et piège du sous-développement au Maroc. / Economic Policy and Underdevelopment Trap in MoroccoYamani, Nezha 14 March 2012 (has links)
L’objet de cette thèse est de tester la pertinence de l’hypothèse du piège du sous développement, en montrant à travers les performances économiques, que la politique de désinflation a installé l’économie marocaine dans un équilibre bas. L’objectif est de mettre en évidence les effets restrictifs sur la croissance et l'emploi, de l'orientation de la politique monétaire et budgétaire. Le cadre conceptuel proposé découle des débats afférents à la règle versus discrétion, à l’indépendance et la crédibilité de la Banque centrale, à la soutenabilité budgétaire et un policy mix coopératif. L'évaluation du policy mix mis en œuvre avec rigueur depuis 1998, s’appuie sur l'articulation de cadres d’analyse issus des théories de la politique économique, de l'économie de la croissance endogène et de l'analyse en termes de capacités d'Amartya Sen. Deux axes de réflexion ont été élaborés. Le premier concerne le rattachement du concept de piège du sous développement à celui de la croissance molle constituant ainsi, les principales caractéristiques du régime de croissance en présentant les contraintes qui pèsent sur l’économie. Le second met l’accent sur l’évaluation du bien-être à partir des opportunités et des libertés offertes par les politiques publiques. Dans ce sens, il est question d’analyser les recoupements qui existent entre la politique économique, le bien-être social et les capacités. Ainsi, le premier des cinq chapitres de la thèse, traite des soubassements théoriques et des mécanismes sous-jacents qui ont guidé le décideur public dans le choix de sa politique économique. Les règles fixes en matière d'inflation et de limitation du déficit public, la coordination du réglage monétaire et de la gestion des finances publiques, l'indépendance de Banque centrale, les réformes structurelles entreprises ainsi que la priorité accordée à la stabilité macroéconomique, attestent et cautionnent les fondements néoclassiques de la politique économique. La recherche de la crédibilité monétaire à travers la règle fixe d'inflation de 2% a conduit à un renchérissement du coût du crédit. Le maintien des taux d’intérêt élevés est à l’encontre des intérêts des PME qui se trouvent pénalisées par le rationnement du crédit dont elles font l’objet. En matière budgétaire, la réduction du déficit public à 3% constitue une règle qui assure la maîtrise des finances publiques et soutient l’Institut d’émission dans sa lutte contre l’inflation. Le respect impératif de cette règle, quels que soient les chocs qui affectent l’économie, entretient les facteurs de blocage liés à la baisse de la demande et du revenu globaux. Le décideur public se prive ainsi, d'actions de redistribution et de régulation de la conjoncture susceptibles de limiter les disparités sociales. La politique de rigueur, de par le coût social qu’elle induit, limite la garantie des droits et des libertés. Le chômage des jeunes, les difficultés d’accès aux biens et services de base, la pauvreté, le sous emploi et l’analphabétisme constituent un manque de libertés et de droits qui restreint l’étendue des choix et des réalisations effectives. Il apparaît, en définitive, que le choix de la politique de rigueur axée sur des règles inflexibles, atteint assurément l’objectif de stabilité macroéconomique, mais au prix d’un déficit de croissance et de bien-être social. Les effets de la crise financière sur l’économie viennent confirmer la fragilité du système de croissance. Celle-ci a transité par des effets de revenus liés à la baisse de la demande externe à travers quatre canaux de transmission: le tourisme, les exportations, les transferts des résidents marocains à l’étranger et les IDE. Les taux de croissance enregistrés entre 2008 et 2010 restent faibles et l’emploi recule. L'impact de la crise met fin à l'illusion de résilience de l’économie et attire l’attention sur le fait qu’il existe une politique alternative axée sur la croissance et l’emploi. / The aim of this research is to test the relevance of underdevelopment trap concept, by showing through the economic performance, that the policy of disinflation has installed the Moroccan economy in a low balance. The purpose is to highlight the restrictive effects on the growth and employment, the orientation of monetary and fiscal policy. The proposed conceptual framework derives from the debates related to the rule versus discretion, independence and credibility of the Central Bank, fiscal sustainability and a cooperative policy mix. The evaluation of the policy mix implemented with rigor since 1998 is based on the articulation of analytical frameworks from the theories of the economic policy, the economy of the endogenous growth and analysis in terms of capabilities of Amartya Sen. Two lines of thought have been developed. The first one involves the incorporation of the concept of underdevelopment trap to the sluggish growth thus constituting, the main characteristics of the system of growth in presenting the constraints on the economy. The second puts the evaluation of the welfare on the opportunities and freedoms offered by public policies. In this sense, it is necessary to analyze the inferences that exist between the economic policy, social welfare and the capabilities. These analyzes have mobilized multiple empirical data in order to assess the contradictory factors that prevent the economic activity from achieving its potential growth. Thus, the first five chapters of the thesis deals with theoretical foundations and the underlying mechanisms that guided the policy makers in the choice of its economic policy. The fixed rules in regard to inflation and the limitation of public deficit, the coordination of monetary setting and for the management of public finances, the independence of the Central Bank, the structural reforms as well as the priority given to macroeconomic stability, attest and endorse the neoclassical foundations of the economic policy. Seeking monetary credibility through the fixed rule of 2% inflation led to an increase in the cost of credit. Indeed, maintaining high interest rates is counter to the interests of SMEs which are penalized by the rationing the amount of credit that they are the subject. In budgetary matters, reducing the deficit to 3% constitutes a rule that ensures the control of public finances and supports the issuing institute in its fight against inflation. The imperative respect for this rule, regardless of the adverse shocks that affect the economy, maintains the factors of blocking linked to the decline in demand and the global income. Public Decision makers are thus deprived the shares of redistribution and to regulate their situation likely to limit social disparities. The strict policy limits the guarantee of rights and freedom because of its resulting social costs. Youth unemployment, the difficulties of access to goods and basic facilities, poverty, underemployment and illiteracy are a lack of freedom and rights that restricts the range of choice and achievements. The growth deficit feeds the social deficit and the extent of inequality strengthens it. It appears, eventually, that the choice of the strict policy focused on inflexible rules ensures, certainly achieved the objective of macroeconomic stability, but at the cost of low growth and welfare. The effects of the financial crisis on the economy just confirm the fragility of the system of growth. The latter has channelled through the effects of income related to the decline in external demand through four channels of transmission: tourism, exports, and transfers from Moroccan living abroad and the IED. The rate of growth recorded between 2008 and 2010 remained low and employment declined. The impact of the crisis puts an end to the illusion of resilience of the economy and draws the attention to the fact that there is an alternative policy focused on growth and employment.
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Měření diverzity koprofágních brouků a jejich půdní aktivity na pastvině / Examination of the diversity and digging activity of dung beetles in pastureANDĚL, Tomáš January 2014 (has links)
The survey of the diversity of coprophagous beetles (Scarabaeidae, Geotrupidae, and Hydrophilidae families) and their soil activity took place at two sites in a cattle pasture in southern Bohemia (site A: 49°29'31.720"N, 14°23'44.310"E; site B: 49°29'23.257"N, 14°23'35.964"E; 575 m a. s. l.). Baited pitfall traps with fresh cow dung (1.5 l per trap) were used to capture the beetles. During the survey of the diversity of coprophagous beetle community, a total of 29 species of beetles numbering 1,189 specimens were captured from May to September 2013. Of these, the most numerous were the beetles of the genus Aphodius, who made up 79 % of the total number of captured specimens. In terms of biomass, Geotrupes spiniger (Marsham, 1802) was significant, in that it made up 24 % of the total biomass of all of the captured beetles. This species contributes most to the decomposition of dung in the pasture. The family with the least number of specimens was Hydrophilidae. Beetles from this family made up 19 % of total number. Measurement of soil activity took place repeatedly over the course of 3 weeks, always after one-week measurement of diversity. The most numerous species (A. fimetarius, A. rufus and A. fossor) showed a linear dependence of the abundances in soil-activity traps on the abundances in diversity traps from the precedent capture period. A. sticticus was one of the most numerous species during surveys of diversity (10 %). This species, belonging to the dwellers group, was not recorded in soil-activity traps, however. Large tunnellers were represented mainly by G. spiniger in traps, for which the linear dependence was not possible to confirm.
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O efeito do contexto da paisagem e da estrutura de habitat sobre abelhas e vespas silvestres em fragmentos de cerrado /Ferreira, Bruno. January 2009 (has links)
Orientador: Maria José de Oliveira Campos / Banca: Marcos Aparecido Pizano / Banca: Marcio Uehara Prado / Resumo: Os requerimentos de habitat necessários para o estabelecimento e sobrevivências de abelhas e vespas solitárias incluem locais e materiais de nidificação, e recursos para forrageio. Este estudo procurou compreender como os recursos oferecidos pelo habitat e pela paisagem podem influenciar na distribuição desses organismos, ao se estabelecerem e se deslocarem por diferentes tipos de uso e ocupação do solo. Foram utilizados ninhos armadilha como método de amostragem, durante um período de 13 meses, em 24 fragmentos de cerrado na região da Bacia do rio Corumbataí. Simultaneamente as mesmas áreas foram analisadas e descritas pelas métricas da Ecologia da Paisagem. O levantamento dos dados biológicos não permitiu nenhuma conclusão dentro dos objetivos propostos, uma vez que o número amostral de indivíduos adultos foi insatisfatório. Entretanto as análises da paisagem permitiram contextualizar a região de estudo com uma paisagem heterogênea e inadequada para o estabelecimento de uma fauna diversificada de abelhas e vespas. Os fragmentos de estudos são geralmente pequenos, pouco conectados e inseridos em matrizes de baixa permeabilidade, contribuindo com a diminuição da diversidade de fauna. Adicionalmente, foi possível organizar as áreas de estudo em níveis de prioridades de conservação, buscando criar caminhos mais práticos para traçar políticas conservacionistas e concentração de esforços. / Abstract: Habitat requirements of solitary bees and wasps include nesting sites, food resources and nesting material. This work attempted to understand how those resources, available in different scales, from habitat to landscape, could drive the distribution of bees and wasps populations over a heterogeneous landscape. For solitary bees and wasps sampling it was used trap-nests, during a 13 months period, on 24 cerrado patches scattered over Corumbataí river basin. Meanwhile, those same areas were analyzed by Landscape Ecology metrics. The biological survey could not allow any further analysis, given an unexpected low rate of nesting individuals. However, landscape analysis described Corumbataí river basin as an inappropriate environment for some trap-nesting bee and wasp species; as well the selected patches, which were usually small, with low connectivity, and merged in a hostile matrix. Besides, it was possible to create levels of "priority conservation", which give decision makers practical choices in environmental policies and efforts. / Mestre
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O efeito do contexto da paisagem e da estrutura de habitat sobre abelhas e vespas silvestres em fragmentos de cerradoFerreira, Bruno [UNESP] 21 December 2009 (has links) (PDF)
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ferreira_b_me_rcla.pdf: 917476 bytes, checksum: ae054d19a346290a51629e619247ffb1 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os requerimentos de habitat necessários para o estabelecimento e sobrevivências de abelhas e vespas solitárias incluem locais e materiais de nidificação, e recursos para forrageio. Este estudo procurou compreender como os recursos oferecidos pelo habitat e pela paisagem podem influenciar na distribuição desses organismos, ao se estabelecerem e se deslocarem por diferentes tipos de uso e ocupação do solo. Foram utilizados ninhos armadilha como método de amostragem, durante um período de 13 meses, em 24 fragmentos de cerrado na região da Bacia do rio Corumbataí. Simultaneamente as mesmas áreas foram analisadas e descritas pelas métricas da Ecologia da Paisagem. O levantamento dos dados biológicos não permitiu nenhuma conclusão dentro dos objetivos propostos, uma vez que o número amostral de indivíduos adultos foi insatisfatório. Entretanto as análises da paisagem permitiram contextualizar a região de estudo com uma paisagem heterogênea e inadequada para o estabelecimento de uma fauna diversificada de abelhas e vespas. Os fragmentos de estudos são geralmente pequenos, pouco conectados e inseridos em matrizes de baixa permeabilidade, contribuindo com a diminuição da diversidade de fauna. Adicionalmente, foi possível organizar as áreas de estudo em níveis de prioridades de conservação, buscando criar caminhos mais práticos para traçar políticas conservacionistas e concentração de esforços. / Habitat requirements of solitary bees and wasps include nesting sites, food resources and nesting material. This work attempted to understand how those resources, available in different scales, from habitat to landscape, could drive the distribution of bees and wasps populations over a heterogeneous landscape. For solitary bees and wasps sampling it was used trap-nests, during a 13 months period, on 24 cerrado patches scattered over Corumbataí river basin. Meanwhile, those same areas were analyzed by Landscape Ecology metrics. The biological survey could not allow any further analysis, given an unexpected low rate of nesting individuals. However, landscape analysis described Corumbataí river basin as an inappropriate environment for some trap-nesting bee and wasp species; as well the selected patches, which were usually small, with low connectivity, and merged in a hostile matrix. Besides, it was possible to create levels of “priority conservation”, which give decision makers practical choices in environmental policies and efforts.
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Détermination du rapport d’embranchement de la transition super-permise du carbone 10 et développement et intégration de la ligne de faisceau PIPERADE au CENBG / Determination of the branching ratio of the superallowed transition of carbon 10 and development of the beam line PIPERADE at CENBGAouadi, Mehdi 15 December 2017 (has links)
Les études de la radioactivité bêta dans les milieux nucléaires permettent en partie de participer à la détermination d’un des paramètres qui décrit l'interaction faible (la constante de couplage vectoriel). Pour cela, de nombreuses mesures permettent déjà d’atteindre de grandes précisions sur ce paramètre pour un grand nombre de noyaux des transitions bêta super-permise. Cependant, pour le carbone 10, l'incertitude relative du rapport d'embranchement reste encore élevée par rapport aux autres noyaux pères avec une valeur de l’ordre de 0,13 %. Ceci est dû à l’énergie du photon émis par l’état 0+ du noyau fils qui est de 1021,6 keV, c’est-à-dire proche de l’énergie d’empilement de deux signaux de photons de 511 keV. En mai 2015, notre groupe a réalisé, à ISOLDE au CERN, une expérience afin de mesurer très précisément cette transition. Pour produire le carbone 10,nous avons réalisé des réactions nucléaires qui produisaient en grandes parties les noyaux d’intérêts mais aussi des contaminants de mêmes masses émetteurs de bêta+. Afin de réduire l’empilement, il aurait été nécessaire de mieux séparer les éléments ou d’estimer celui-ci à partir de données équivalentes avec le néon 19. Ainsi, nous avons calculé une constante d’empilement qui dépend du temps de mise en forme est qui est de l’ordre de 0,1μs. Par la suite, l’analyse de nos données carbone 10 a permis d’obtenir un rapport d’embranchement de 1,500(4) % alors que la moyenne des valeurs de la littérature donne1,4645(19) %. Dans le but de produire plus d’espèces de noyaux et d'augmenter l'intensité des faisceaux, le GANIL (Grand Accélérateur National d'Ions Lourds) développe actuellement un nouvel accélérateur ainsi qu'un ensemble de cibles basées sur la méthode ISOL. Pour réduire le dépôt de contaminants aux points de mesures, tel que c'était le cas pour la mesure du carbone 10 à ISOLDE, la communauté de physiciens souhaite aussi développer un ensemble d'outils de séparations. Dans ce cadre, notre groupe participe depuis 2011 au développement de deux de ces outils : un séparateur de haute-résolution (HRS) pour séparer des noyaux dont le pouvoir de résolution en masse nécessaire (m/Δm) souhaité est de 20000et un double piège de Penning (PIPERADE) pour séparer les noyaux qui nécessite au maximum d’un pouvoir de résolution en masse de 100000. Ainsi, au CENBG, une ligne faisceau de test qui comprend une source d'ions FEBIAD, le quadrupôle radiofréquence regroupeur-refroidisseur GPIB, un aiguillage électrostatique et le double piège de Penning (PIPERADE) est en cours de développement. Lors des tests de ces dispositifs, nous avons observé une efficacité de transmission de l’ordre de 80 % du faisceau qui traverse le GPIB.Également, nous avons mesuré une émittance transverse de 3 pi.mm.mrad en comparaison de celle de 26 pi.mm.mrad observées en aval du GPIB. Par la suite, les simulations de laligne d’injection dans le piège de Penning ont permis de définir une décélération qui permet d’injecter 98 % des ions extraits du GPIB.Cette thèse se compose donc de deux parties : la détermination du rapport d'embranchement du carbone 10 et le développement et l'intégration au CENBG de la ligne de faisceau PIPERADE. / The beta radioactivity studies in nuclear medium allow to participate in thedetermination of one of the parameters that describes the weak interaction (the vectorcoupling constant). For this purpose, numerous measurements have already been made todetermine this parameter with great precision for superallowed transition nuclei. However,for carbon 10, the relative uncertainty of the branching ratio is still high compared to otherparent nuclei with a value of the order of 0.13%. This high uncertainty is due to photonenergy emitted of 1021.6 keV which is really closed to the energy due to pile-up of twophotons of 511 keV. In May 2015, our group conducted an experiment at ISOLDE at CERN tomeasure the branching ratio very precisely. The nuclear reactions needed to produce thenuclei gave a large amount of nuclei of interest but also contaminants of the same massewhich also emit beta+ particles. A pile-up ratio of around 0.1 μs was calculated. Then, wefound a branching ratio of 1.500(4) % whereas the average from litterature is 1.4645(19) %.To study more species of nuclei and increase the intensity of the beams, GANIL(Grand Accélérateur National d’Ions Lourds) is currently developing a new accelerator as wellas a set of targets based on ISOL method. In order to reduce the contaminants deposit atthe measurement points, as we saw for the measurement of carbon 10 at ISOLDE, thecommunity of physicists also wants to develop separation apparati. In this context, since2011, our group has been involved in the development of two of these tools: a highresolutionseparator (HRS) to separate nuclei which need a mass resolving power (m / Δm)around 20,000 and a double Penning trap (PIPERADE) to separate the nuclei which require amaximum resolution of 100,000. Thus, at CENBG, a test beam line that includes a FEBIAD ionsource, a RFQ cooler-buncher (GPIB), an electrostatic switch, and a double Penning trap(PIPERADE) is under development. During apparati tests, we observe a transmissionefficiency around 80 %. Also, we measure a transverse emittance about 3 pi.mm.mrad whichis lower than 26 pi.mm.mrad observed before the GPIB. By the way, simulations of the beamline permitted to decelerate the beam and inject 98 % of ions.This thesis consists of two parts: the determination of the carbon 10 branching ratioand the development and integration of the PIPERADE beam line at CENBG.
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Prostorová distribuce vodních ploštic (Heteroptera: Nepomorpha) v rybářsky obhospodařovaných rybnících: odhad a srovnání na základě výsledků dosažených klasickou metodou odchytu (cedníkem) a metodou světelných pastí / Spatial distribution of water bugs (Heteroptera: Nepomorpha) in fishponds: estimation and comparison based on results reached by classic method (netting) and method of light traps.ČELOUDOVÁ, Monika January 2009 (has links)
The aim of this methodically oriented thesis was to find spatial distribution of water bugs in fishpond by parallelly used two different sampling methods - classic method (netting) and light traps as well as to find, if sampling method can influence a result of ecological study by substantial way. Study was realized in the one locality - fishpond Polepšil (region: Vysočina: Moravskobudějovicko) in years 2007 and 2008. Spaces {--} transects for sampling were difined. Efficiency of water bug sampling by nett is conspicuously less than sampling by light traps. More species and individuals (in total sum of samples and in samples from individual transects too) were sampled by light traps under comparable conditions. Chemical yelow-green light of light traps was more attractive for water bugs than the pink one. Spatial preferences of some corixid species and their developmental stages were noted by application of light trap method of sampling. Light trap method of samplings brings more complete and valuable data for ecological studies of water bug communities.
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Multielectron Bubbles : A Curved Two-dimensional Electron System in ConfinementJoseph, Emil Mathew January 2017 (has links) (PDF)
Electrons are weakly attracted to liquid helium due to the small but finite polarizability of helium atoms. However, they cannot enter the liquid unless their energy is more than 1 eV, due to the Pauli exclusion principle. As a result, electrons are bound perpendicular to the surface but are free to move parallel to the surface i.e., they form a two-dimensional electron system (2DES). If the electron density of the 2DES is increased above a critical value ( 1013 per m2) the surface becomes un-stable leading to the formation of charged bubbles known as multielectron bubbles (MEBs). In MEBs the electrons are confined to the inner bubble surface and hence we have a 2DES on a curved surface.
The critical density of electrons on the bulk surface is too low to study the quantum dominated phases of the 2DES. In contrast, due to the enormous surface defects and impurities, the electronic density of 2DES in semiconductors cannot be lowered below 1015 per m2, which is high enough such that the 2DES is always in a quantum liquid phase. Alternatively, the possibility of varying the electron density over a wide range and the effects of curvature implies that MEBs can be used to probe new phases of 2DES like Wigner crystallization with strong electron-ripplon coupling, quantum melting, superconductivity etc.
In this thesis the experiments done on MEBs in liquid helium are described. In the initial experiments we generated MEBs which were observed to shrink in size. We saw a difference in their collapse behaviour: MEBs in super fluid helium though initially bigger in size collapse much faster than MEBs generated in normal fluid. The vapour present in the MEBs cannot condense fast in normal fluid due to the lower thermal conductivity. In subsequent experiments, we could trap these MEBs, generated in normal fluid and stabilised by their vapour content, in a linear Paul trap. We measured the charge and radius of these trapped MEBs by analysing their dynamics. Interestingly, the stably trapped MEBs were found not to lose charge as they shrink and disappear in hundreds of milliseconds, implying that the charge density inside increases at least two orders of magnitude from the initial value. MEBs so trapped can be used to study the properties of 2DES in the high electron density limit where the quantum confinement energy dominates.
Later, we measured the charge of the MEB with respect to time when it was held on a solid substrate. We propose a charge loss mechanism as the tunneling of electrons across a thin lm of helium formed between the MEB and the substrate. We estimated the density of electrons on this thin lm by using a numerical model. We found that the maximum electron density (about a few 1015 per m2) which could be held on a thin lm is limited by tunneling. Moreover, the substrate surface roughness did not affect the charge loss due to the microscopic contact of MEBs with the substrate, resolving the complications in charge loss observed in previous experiments on macroscopic thin films on metallic substrates. Finally, we describe the experiments and the results on the stability of MEBs generated in super fluid helium. Highly charged MEBs (with more than 104 electrons which have an equilibrium radius that is easily visible) are found to be unstable against fission into smaller bubble showing a type of electro-hydrodynamic instability. However, the stability of bubbles with radius less than our detection limit ( 1 m) is still an open question.
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Preparação de laser de diodo e sua utilização em aprisionamento e estudo de átomos frios / Preparation of diode laser and its use in trapping and study of cold atoms.Aparecida Marika Tuboy 05 July 1996 (has links)
Este trabalho relata o desenvolvimento de todo o aparato experimental para a realização de aprisionamento de césio através de uma armadilha magneto-óptica. As fontes de luz neste processo foram os lasers de diodo e todo seu sistema para operação, estabilização e redução da largura de linha foi construído. As medidas das constantes de mola e amortecimento foram realizadas como função dos parâmetros característicos das armadilhas de césio e de sódio. Também realizamos outros experimentos com átomos aprisionados de sódio na presença de duas freqüências, linha D1 e D2. A primeira medida constitui na obtenção da taxa de colisões entre átomos aprisionados na linha D1 e depois foi realizado observações de uma nova estrutura operando neste regime. / This thesis describes the development of a complete experimental setup for trapping cesium by a magneto-optical trap (MOT). In this work we have employed diode lasers as light sources and built the entire system for their operation, stabilization and linewidth reduction. We have measured the MOT spring and damping constants as functions of the characteristic parameters of the cesium and sodium traps. We have also carried out two other experiments on trapped sodium atoms operating in the simultaneous presence of the D1 and D2 line frequencies. The first experiment has established the collision rate of trapped atoms in the D1 line MOT and the second has allowed us to observe a new structure operating in this two-frequency regime.
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Produção de moléculas frias heteronucleares no estado fundamental / Production of ground state cold heteronuclear moleculesMarília Wellichan Mancini 21 November 2003 (has links)
Neste trabalho apresentamos a produção de moléculas frias heteronucleares em uma armadilha magneto-óptica mista de 39K e 85Rb e detectadas no estado fundamental. A técnica de detecção consiste na fotoionização pulsada das moléculas que, após terem sido fotoassociadas, decaem através de emissão espontânea para estados ligados do potencial do estado molecular fundamental. A partir dos resultados da produção de moléculas frias KRb, estudamos-as com relação ao tipo de colisões que as originam, e à temperatura associada ao seu movimento translacional. Experimentos foram também realizados para comprovar que as moléculas detectadas são provenientes do estado fundamental. Finalmente, também estudamos neste trabalho, a taxa segundo a qual são formadas. Concomitantemente à produção de KRb, moléculas frias homonucleares 39K2 e 85Rb2 são também formadas, detectadas e caracterizadas. São apresentados também, os primeiros passos dados em direção à realização de espectroscopia fotoassociativa dos estados ligados das moléculas heteronucleares obtidas. / In this work, cold ground-state KRb molecules were produced by photoassociation in a two species magneto-optical trap (MOT) containing 39K and 85Rb. The KRb molecules are produced through photoassociation and detected in the ground state by multiphoton pulsed ionization. We have characterized their translational temperature and measured their formation rate constant. Homonuclear cold molecules 39K2 and 85Rb2 detected in their ground state were also formed in our trap and characterized as well. It is also reported our first efforts towards the realization of photoassociation spectroscopy of the heteronuclear molecules produced in our trap.
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