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SEMINARIO DFI Extraordinario: Charge Transport on a Single Molecule Level |
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Expositora: Diana Dulić Kavli Institute of Nanoscience, Delft University of Technology, The Netherlands Martes 10 de julio, 14:30 h Av. Blanco Encalada 2008, 3er piso Sala de Seminarios ***NOTAR CAMBIO DE FECHA*** Abstract: Building an electronic device using individual molecules is one of the ultimate goals in nanotechnology. To achieve this it will be necessary to measure, control and understand electron transport through molecules attached to electrodes. Although some devices have already been realized, a number of fundamental questions, such as: “What is the nature of transport through these systems, and how can we employ and tune their electrical properties for new electronic devices?” have not been answered yet. A central problem, common for all of them is: “How to reliably connect a nano-object to the macroscopic world?” The conductance of a molecule depends not only on its intrinsic properties, but is very sensitive to the atomic level details of the molecule-electrode contact and the local environment of the molecule. I will show several examples of influence of metal-molecule contacts obtained with mechanically controllable break junctions (MCBJ) method which is a reliable technique for obtaining a single molecule junction. For instance, of how an intrinsically light switchable molecule may lose its functionality after it is contacted to the electrodes and how it can regain the functionality by adjusting the molecular structure. I will present an overview in the development of the MCBJ technique in the past ten years and some recent advances, such as mechanically tuning of the electronic transport in a porphyrin molecule. |
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SEMINARIO DFI: Procesos de reciclaje superficial de haluros (Cl, I) y metales preciosos (Au, Ag) en |
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Expositor: Martín Reich Departamento de Geología Viernes 29 de junio, 16 h. Av. Blanco Encalada 2008, 3er piso Sala de Seminarios ***NOTAR CAMBIO DE SALA*** RESUMEN: El enriquecimiento supérgeno de Cu en el Desierto de Atacama tradicionalmente se modela como un proceso de disolución y re-precipitación de sulfuros, óxidos , sulfatos e hidroxicloruros de Cu, por efecto de aguas superficiales en una escala de tiempo estrictamente comprendida entre los 45 y 15 millones de años. En este seminario mostraré los resultados obtenidos a lo largo de los últimos 5 años de investigación, y que llevan a los siguientes cambios de paradigma del modelo: (i) El solvente que generó la disolución no fue exclusivamente agua dulce, sino también agua salina profunda; (ii) El proceso de disolución/re-precipitación se extiende más allá del límite propuesto (15 Ma), hasta la actualidad, y (iii) El proceso de disolución/re-precipitación generó, aparte del enriquecimiento de Cu, concentraciones anómalas de metales preciosos y metaloides (Au, Ag, As) en forma de nanopartículas. Estas conclusiones se apoyan en datos obtenidos mediante técnicas microanalíticas de alta resolución (microscopía electrónica de transmisión, microsonda electrónica), métodos isotópicos (espectrometría de masas por ICP, espectrometría de masas por aceleración, espectrometría de masas por ionización secundaria) y modelamiento geoquímico.
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SEMINARIO DFI: Quantum and thermal fluctuations in an ultracold 1d bose gas |
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Expositor: Julien Armijo Departamento de Física Facultad de Ciencias Viernes 22 de junio, 16 h Av. Blanco encalada 2008, 3er piso Sala de Seminarios ***notar cambio de sala*** Abstract: In this seminar, I will present recent results otained at Institut d'optique, Palaiseau, France. Using micro-magetic traps on an "atom chip", we capture and cool 87Rb atoms to ultralow temperatures (~10nK). Quantum degeneracy is reached when the de Broglie wavelength of atoms becomes larger than the interparticle distance. Then, we take absorption images of the "quantum gas" and, using hundred of pictures, we carefully analyse the fluctuations of atom number in each imaging pixel. Firstly, we use density fluctuations as a precise probe for the thermodynamics of the gas, and we explore the rich phase diagram of repulsive 1D bosons, where the quantum statitical tendency of bosons to "bunching" competes with interparticle repulsion, which pushes towards anticorrelations. In particular we map out the "quasicondensation" transition, the analogue of Bose-Einstein Condensation in 1D. Secondly, at record low temperatures, we demonstrate the microscopic observation of quantum fluctuations, directly in each single picture, for the first time in a continuous system. |
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Seminario DFI: Fourier Transform Infrared spectroscopy and vacuum techniques practical applications |
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Expositor: Jean-Francois Veyan Materials Science and Engineering department, University of Texas at Dallas.Texas, USA. Viernes 15 de Junio, 16 h Av. Blanco Encalada 2008, 3er piso Sala de Seminarios ***NOTAR CAMBIO DE SALA*** Resumen: Fourier Transform Infrared (FT-IR) spectroscopy can be performed in many different ways: transmission, reflection, attenuated total reflection (ATR), multiple internal reflections (MIR), and others even more complex. To illustrate the power of these techniques, I will discuss three recent examples of research breakthroughs: (i) the reaction pathways between a disilane (Si2H6) molecule and a Si(100)-(2x1) surface, (ii) the first observations of the spill-over of H on a Ti-doped Al(111) surface, and (iii) Hydrogen interaction with Metal Organic Frameworks (MOFs). These findings are significant because they impact important current practical applications involving atomically precise manufacturing of quantum dots for data storage, and hydrogen storage for advanced automotive applications |
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