Neste trabalho reportamos a produção da primeira armadilha magneto-ótica que confina simultaneamente duas espécies atômicas distintas: Sódio e Potássio. Para podermos realizar este aprisionamento, foi necessário vencer algumas dificuldades técnicas que justificam, inclusive, a escolha dos elementos utilizados. Nossa armadilha também foi utilizada para realizar o primeiro estudo de colisões frias entre átomos de espécies diferentes. Experimentalmente, as informações sobre essas colisões são obtidas através da medida da dinâmica de perdas da armadilha de S6dio em presença e ausência de átomos frios de Potássio. Observamos que o efeito de colisões heteronucleares e dez vezes menor do que as homonucleares. Esta diferença já era esperada devido ao menor alcance dos potenciais de interação entre átomos no caso de espécies distintas. Nossos resultados são comparados a uma teoria semi-clássica simples e se encontram em bom acordo com as previsões. Introduzimos uma nova técnica que consiste em mudar repentinamente a intensidade do laser aprisionador e observar a variação do número de átomos aprisionados. Medimos a taxa de perdas por colisão entre átomos de Potássio frios como função da intensidade do laser aprisionador. Essa técnica nos permite alcançar o regime de baixas intensidades, inclusive abaixo da intensidade de saturação, sem as limitações da técnica tradicional. Aplicamos essa técnica ao aprisionamento simultâneo e medimos a taxa de perdas por colisão do sódio na presença e ausência de potássio. Com essa medida somos capazes de estimar a seção e choque entre sódio e potássio ambos no estado fundamental / In this thesis we report the production of the first magneto-optical trap that confines simultaneously two atomic species, sodium and potassium. In order to realize this experiment we had to overcome some technical difficulties that justified our choice of these two elements. This trap was used to study cold collisions between two different species. The information about these collisions is obtained experimentally from the dynamics of the sodium trap loss process in the presence and absence of potassium atoms. We observed that the heteronuclear effect is ten times smaller than the homonuclear one. This difference is explained by the smaller range of the interaction potentials between different species. Our results are compared with the theoretical predictions of the semi-classical theory and show a good agreement with the predictions. We have introduced a new technique which consists of a sudden decrease of the laser intensity, after which we observe the temporal variation in the number of trapped atoms. We have measured the loss rate coefficient between cold potassium atoms as a function of light intensity of the trapping laser. This technique allowed us to reach the very low intensity regime, as low as 30% of the saturation intensity, without compromising the loading process. We applied this technique to the simultaneous trapping and measured the loss rate coefficient between cold sodium atoms in the presence and absence of cold potassium atoms. With this measurement we can estimate the value of the cross section between sodium and potassium in the ground state

Neste trabalho pela primeira vez, desaceleramos um feixe de Cs pela Técnica de Sintonia Zeeman. Usamos um laser de diodo contrapropagante ao feixe atômico. Essa técnica se baseia na utilização de um campo magnético de perfil espacial parabólico para compensar o efeito Doppler e manter o átomo ressonante com o laser durante o processo de desaceleração. Conseguimos reduzir a velocidade dos átomos até C 940cm/s. Para medir essa velocidade usamos uma técnica simples, diferente da usual, que utiliza um feixe de prova. Com o nosso magneto, não foi possível desacelerar átomos com velocidade acima de 12000 cm/s. O limite de campo magnético em que tivemos que trabalhar corresponde à campo fraco, para o estado fundamental do Cs. Esse fato acarreta um aumento na probabilidade de ocorrerem transições erradas. Observamos a presença de um intervalo de \"detuning\" útil, fora do qual não conseguimos desacelerar. Esse intervalo também está relacionado com o limite máximo de velocidades para que haja desaceleração. Chegamos a esse intervalo através de simulações feitas para encontrar os parâmetros necessários à desaceleração. Os resultados obtidos experimentalmente estão de acordo com o que foi previsto pela simulação. Paralelamente à desaceleração de CS, preparamos os lasers de diodo e reduzimos sua largura de linha. Entretanto não usamos o laser estreito para a desaceleração. A fim de trabalharmos com espectroscopia de alta resolução reduzimos a largura de linha do laser a semicondutor fazendo um acoplamento da cavidade laser com uma cavidade, Fabry-Pérot, externa. Conseguimos estreitar a largura de linha até 500KHz. Esse resultado nos possibilitará investigar as linhas do Cs, aprisionado em um \"trap\" magnético-óptico, experimento este que já está em andamento em nosso laboratório / In this work for the first time, slow a beam of Cs by the Zeeman tuning technique. We use a laser diode contrapropagante the atomic beam. This technique is based on the use of a magnetic field of parabolic spatial profile to compensate for the Doppler effect and keep the atoms resonant with the laser during the downturn. We reduce the speed of C atoms to 940cm / s. To measure this speed we use a simple technique, different from the usual, which uses a beam of evidence. With our magnet, could not slow down atoms with speeds up to 12,000 cm / s. The limit of magnetic field we had to work corresponds to the weak field for the ground state of Cs. This fact implies an increase in the probability of transitions wrong. We observed a range of \"detuning\" useful, out of which we cannot slow down. This range is also related to the maximum speed for there to be slowing. We arrived in this range through simulations to find the parameters needed for deceleration. The results obtained experimentally are in agreement with what was predicted by the simulation. Parallel to the slowdown of CS, we prepared the diode lasers and reduced its line width. However do not use the laser close to the slowdown. In order to work with high-resolution spectroscopy reduced the line width of the semiconductor laser causing a coupling of the laser cavity with a cavity, Fabry-Pérot, external. We narrow the line width up to 500KHz. This result will enable us to investigate the lines of Cs, trapped in a \"trap\" magneto-optical experiment that is already underway in our laboratory

Estudamos, de uma maneira sistemática, o campo hiperfino de contacto em átomos livres a fim de analisar a qualidade das funções de onda obtidas a partir da aproximação do operador de massa, da teoria de muitos corpos. 0 campo de contacto depende diretamente da função de onda dos eléctrons na origem e a aproximação utilizada para calculá-lo leva em conta tanto a dependência do exchange com a energia cinética do elétron quanto a inclusão da correlação coulombiana eletrônica, sem necessidade de parâmetros ajustáveis. Observamos que os resultados encontrados para tais campos, como esquema proposto, são competitivos com os de Hartree-Fock e por ser um esquema mais simples pode substituí-lo na obtenção de grandezas físicas relacionadas com as funções de onda dos sistemas a serem estudados. / The hyperfine contact field for free atoms has been calculated within the framework of the mass operator approximation for various atoms, in order to analyze the quality of the electronic wave functions. The mass operator approximation takes into account the electron-correlation effects as well as the dependence of the exchange with the velocity of the electrons. We found that the mass operator approximation to the exchange correlation effects yields values for the hyperfine contact field in good agreement with those obtained through the Hartree-Fock scheme. However, the mass operator approximation is simpler than the Hartree-Fock operator.

Orientador: José Antonio Roversi / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-18T22:02:19Z (GMT). No. of bitstreams: 1 GonzalezHenao_JulioCesar_M.pdf: 3018273 bytes, checksum: 8a7504d4a51886c5befb08df936170c0 (MD5) Previous issue date: 2011 / Resumo: Nesta dissertação estudamos um sistema formado por dois íons de dois níveis aprisionados em cavidades ópticas acopladas, onde analisamos a transferência de estados de dois qubits a partir dos graus de liberdade (de movimento unidimensional e dos estados internos) de um dos íons para o outro. Para o acoplamento entre as cavidades consideramos dois mecanismos diferentes: (1) onde acoplamento é dado pela sobreposição dos campos (acoplamento direto) e (2) via fibra óptica. Em ambos casos foram utilizadas aproximações onde participam apenas um ou dois modos normais coletivos na transferência do estado. Tambem observamos que , na aproximação com dois modos normais, uma melhor transferência dos qubits no sistema acoplado por fibra óptica, quando é comparado com o sistema acoplado diretamente. Por último, estudamos, na aproximação com um só modo normal de transferência, os efeitos de reservatórios térmicos sobre a transferência dos qubits no sistema de íons aprisionados em cavidades acopladas via fibra óptica. Tais reservatórios foram representados pelos processos de emissão espontânea e flutuações na armadilha a temperaturas T = 0. Os resultados mostram que os reservatórios geram perdas na fidelidade da transferência dos qubits / Abstract: In this work we studied a system consisting of a pair of two-level trapped ions in coupled optics cavities, where we analyze the transfer of states of two qubits from the degrees of freedom (of movement and of internal states) of one ion to another. For the coupling between the cavities we consider two different mechanisms: One where the coupling is given by the overlap of the fields (direct coupling) and one optical fiber. In both cases we use aproximations in which only one or two collective normal modes are envolved in the transfer of the state. From these calculations we have noted that in the aproximations with two normal modes a better transfer of the qubit in the system coupled by optical fiber, compared with the system connected directly. Finally, we studied the effects of thermal reservoirs in system of trapped ions in cavities coupled via optical fiber in the proximity of the one normal mode transfer. These reservoirs represent the processes of spontaneous emission and fluctuations in the trap for T = 0 / Mestrado / Física / Mestre em Física

We revisit the proposed extended Schmidt law, which posits that the star formation efficiency in galaxies depends on the stellar mass surface density, by investigating spatially resolved star formation rates (SFRs), gas masses, and stellar masses of star formation regions in a vast range of galactic environments, from the outer disks of dwarf galaxies, to spiral disks and to merging galaxies, as well as individual molecular clouds in M33. We find that these regions are distributed in a tight power law as Sigma(SFR) proportional to (Sigma(0.5)(star)Sigma(gas))(1.09), which is also valid for the integrated measurements of disk and merging galaxies at high-z. Interestingly, we show that star formation regions in the outer disks of dwarf galaxies with Sigma(SFR) down to 10(-5) M(circle dot)yr(-1) kpc(-2), which are outliers of both the Kennicutt-Schmidt and Silk-Elmegreen laws, also follow the extended Schmidt law. Other outliers in the Kennicutt-Schmidt law, such as extremely metal-poor star formation regions, also show significantly reduced deviation from the extended Schmidt law. These results suggest an important role for existing stars in helping to regulate star formation through the effect of their gravity on the midplane pressure in a wide range of galactic environments.

The temperature dependence of the reactions of halogen atoms Cl and Br with SiH4 and (CH3)3SiH have been investigated with the flash photolysis-resonance fluorescence technique. CCI4 and CH2Br2 were used as precursors to produce Cl and Br atoms, respectively. Experiments gave {k(Cl + SiH4) (295 - 472 K)} = (1.56 +0.11) x 10-1 exp[(2.0 + 0.2) kJ mol'/RT] cm3 s4, {k(Br + SiH4)(295 - 575 K)} = (9.0 + 1.5) x 10-" exp[-(17.0 + 0.6) Id mol'/RT] cm3 s', {k(Cl + (CH3)3SiH)(295 - 468 K)} = (1.24 0.35) x 104 exp[(1.3 + 0.8) Id mol4/RT] cm3 s', and {k(Br + (CH3)3SiH)(295 - 456 K)} = (7.6 + 3.3) x 1010 exp[-(28.4 + 1.3) Id mol'/RT] cm3 s'. The results were compared with values from earlier work.

This thesis provides a summary of the laser system constructed in the Quantum Degenerate Gases Laboratory for laser cooling and trapping of 85/87Rband 6Li as well as of experiments that have been pursued in our lab to date. The first chapter provides an overview of the experimental focus of the QDG lab. The second and third chapters provide the fundamental theory behind laser cooling and trapping. The fourth chapter provides details of the laser system. The fifth chapter describes an experiment performed on the subject of dual-injection, performed in collaboration with Dr. James Booth of the British Columbia Institute of Technology (BCIT) involving the dual-injection of a single slave amplifier. The last chapter describes the progress made on the experimental setup needed for the study of Feshbach resonances between 85/87Rb and 6Li and the photoassociative formation of molecules. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

La mécanique quantique a révolutionné la compréhension du monde microscopique depuis son avènement au XXe siècle. Cependant, les propriétés de la matière condensée restent difficiles à étudier en raison d'une puissance de calcul insuffisante pour simuler numériquement les systèmes à N corps. Une approche alternative consiste à piéger des atomes froids dans des réseaux, dont le comportement est analogue à celui des électrons dans un cristal. Ce système modèle, dont les paramètres peuvent être contrôlés, permet de simuler les phénomènes étudiés.La technique usuellement employée pour confiner les atomes ultrafroids dans un réseau consiste à produire une onde stationnaire résultant de l'intérférence entre deux faisceaux contrapropageants. L'originalité du projet dans lequel s'inscrit cette thèse est de générer un potentiel sublongueur d'onde grâce à la modulation des forces de Casimir au voisinage d'une surface nanostructurée. Le confinement des atomes dans un réseau bidimensionnel avec une faible distance intersite (typiquement 50 nm) permettra ainsi de mieux appréhender les propriétés des matériaux, tels que le graphène.Le travail réalisé au cours de mon doctorat s'est ainsi articulé autour de quatre axes. Tout d'abord, le refroidissement d'atomes de Rubidium 87 a été effectué jusqu'à obtenir un condensat de Bose-Einstein. Puis, des simulations numériques ont été réalisées pour mettre en place une nouvelle méthode d'imagerie sublongueur d'onde, s'appuyant sur le couplage différencié des niveaux atomiques avec un double réseau. Ceci permettra d'activer de façon sélective les sites à détecter pour localiser les atomes avec une précision sublongueur d'onde. Un nouveau système d'imagerie a d'ailleurs été développé pour mieux résoudre les images des distributions atomiques. D'autre part, des simulations numériques ont été réalisées pour anticiper les résultats expérimentaux sur le transport adiabatique au voisinage d'une surface. Enfin, dans le cadre de ma convention CIFRE, une nouvelle architecture laser sera présentée, dans le but d'intéragir avec les atomes de potassium 40 qui seront à refroidir dans la suite du projet dans lequel s'inscrit ma thèse. / Quantum mechanics was a revolution for microscopic systems understanding. However, the study of many-body systems remains a challenge because of computation complexity. Ultracold atoms trapped in lattices offer an alternative way to simulate condensed matter properties. Indeed, their behaviour is similar to the one of electrons in crystals.The common approach for generating optical lattices is to make two laser beams interefere so that we can get a stationary wave that reproduces the potential wells of the crystalline structure. In the new ongoing project, the lattices will be produced by modulation of Casimir-Polder forces nearby a nanostructured surface. Ultracold atoms trapped in a 2D lattice with a short lattice spacing (50 nm) will enable a better understanding of material properties (e.g. graphene).The work I have done during my thesis can be split into in four parts. The first one consisted in cooling Rubidium 87 until Bose-Einstein condensate regime. Then, numerical simulations were performed to set up a new subwavelength imaging technique, based on different couplings between atomic levels with a double lattice. This will make it possible to activate the sites selectively, in order to pinpoint the atoms with subwavelength precision. Moreover, a new imaging system was developped to improve the resolution of the atomic cloud images. I did new calculations in order to predict experimental results on adiabatic atomic transport in the near field of a surface. Finally, a new laser architecture was designed in this thesis, as part of CIFRE convention, in order to cool down potassium 40 atoms, which has to be done in the future.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22824号 / 理博第4634号 / 新制||理||1666(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 川上 則雄, 教授 高橋 義朗, 教授 石田 憲二 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

This dissertation summarizes my research in the Roy group on the development, synthesis, and study of new N-heterocyclic carbene (NHC) based ligands and nickel phsophinidene core compositions of molecular clusters, also known as superatoms. Chapter 1 introduces superatoms as atomically precise and discreet building blocks for use in the design and synthesis of novel materials. A brief history as well as selected synthetic strategies of superatoms will be introduced. The relevant materials properties of superatoms as well as their dependence on core composition and ligand structure will be discussed. Next, the use of superatoms with specialized or functionalizable ligands to synthesize new materials will be demonstrated. This chapter details the importance of the superatom ligands and core composition is the foundation that the subsequent chapters builds upon in developing these two areas. Chapter 2 introduces a functionalized NHC as a potential superatom ligand. While not necessary for all superatom ligands, ligands that enable electronic access to the superatom core are attractive. In this chapter, the conductance of potential NHC based ligands are probed through the scanning tunneling microscope-based break-junction (STM-BJ) method. A novel method of forming single molecule junctions in situ was used and these ligands are found to display a length dependent conductance with strong coupling to the Au electrode, confirming their potential use as ligands for superatoms. Chapter 3 describes the nature of the NHC–M bond in self-assembled monolayers (SAMs) on a Au(111) surface using high-resolution spectroscopy and theoretical calculations. This study was performed as a result of challenges and questions encountered during the work of Chapter 2. The results obtained from this study explore an important structure-function relationship of NHC ligands and have broader impact in materials chemistry beyond superatoms. Chapter 4 explores the synthesis of superatoms with NHC ligands beyond simple imidazolium-based NHCs. This chapter describes the two primary synthetic techniques used and the synthesis of NHC-ligated superatoms. This work is also ongoing and characterization is limited to crude single crystal X-ray diffraction structures and select NMRs. Finally, Chapter 5 details the use of uncommon organocyclophosphine reagents to synthesis novel nickel-phosphinidene molecular clusters, a potential new superatom. In this chapter the synthesis of a family of nickel-phosphinidene molecular clusters is described and studied. A potential application of these molecular clusters is explored through the thermolytic conversion to the industrially relevant Ni2P.