Examinando por Materia "Espectroscopia de reflectancia"
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Ítem Caracterización y optimización de resonancias plasmónicas en sistemas multicapasPalencia Barrera, Liseth Daniela; Herreño Fierro, César AurelioSurface Plasmons (PS) are collective oscillations of free electrons of a metal, also called oscillations of plasma density. These oscillations are strongly confined to the surface and are associated with an evanescent electromagnetic wave. These properties are related to an exceptional increase in the amplitude of the electric field. This work includes a series of studies in which systematically the structure parameters of a multilayer system are controlled to characterize plasmonic resonances. The results allow to identify the excitation of different plasmonic modes that derive a controllable effective optical response, with application potential to the design of materials.Ítem Cuantificación del contenido de arcilla en los suelos del estado de Santa Catarina, Brasil a través de los datos espectrales obtenidos mediante fieldspec pro 3Estrella Medina, Shirly Vanessa; Jácome Medina, Nataly; Fernández Gómez, Wilmar DaríoThe study of soils is essential in the planning and development of territories. Acquisition of data during soil studies can be difficult due to factors such as the accessibility to terrains and limited resources; for this reason, it is necessary to explore new technologies. Reflectance spectroscopy techniques have proven to be faster, less expensive, and less polluting compared to traditional methods used in analysis of soils. The characterization of the 1534 samples of soils of the State of Santa Catarina - Brazil was based on the interpretation of multi-spectral curves also a model was created to quantify clay based on the regression of the partial least squares (PLSR). Using elements of statistics the established model was found to be optimum to quantify the clays of this region. It was possible to discriminate different soil textural classes through Principal Component Analysis (ACP). The development of spectral libraries provides spectral patterns aiding the quantification of physico-chemical attributes of soils.Ítem Perfil de campo eléctrico en estructuras multicapaTriana Guerrero, Paula Andrea; Herreño Fierro, César AurelioThere are several natural systems that can be modeled as multi-layer systems. The skin, the earth's crust, biological systems such as the mitochondria, are just some practical examples. Perhaps, the main interest in multilayer systems is the development of new materials with physical properties on demand. In particular, in relation to optical properties, the design of suitable structures with multiple layers made of different materials has allowed the design of materials with extraordinary optical responses. On the other hand, recent advances in nanofabrication have allowed access to additional degrees of freedom in the design of such structures by exploiting new properties that arise only in this scale. Of particular interest have been the metallic nanostructures where optical excitations take place giving rise to extraordinary phenomena that involve a strong confinement of the electric field to the surface of such nanostructures with innumerable practical applications. These optical excitations are associated with collective oscillations of the free electrons of the metal called surface plasmons. Depending on the type of metallic structures supporting this type of excitations, localized surface plasmons are conceived for the case of isolated metal structures (nanoparticles), and propagating surface plasmons (SPP) for the case of ultra-thin continuous layers. These optical excitations have associated unusual absorptions that can be controlled by manipulating the structural properties. In this way multilayer structures allow to conceive a mechanism of control of these excitations and consequently of the effective optical properties of the structures that support them.Ítem Plasmones superficiales en estructuras multicapa de metales noblesLeón Montañez, Yerson Hernando; Herreño Fierro, César AurelioIn the present work, the reflectance functions are deduced analytically when there is a generation of superficial plasmons in multilayer optical systems. The studied system is known in the literature as the Kretschmann configuration, although there are other configurations, this one is chosen because of his ease on some experimental procedures. This analytical deduction is performed with the help of a stronger mathematical formalism known, as the Transfer-Matrix Method (TMM). This formalism is very powerful because it simplifies a lot the theoretical calculations. TMM is applied to an optical system to deduce the reflectance functions and in this way simulate through computer tools various combinations of metals and dielectrics to study their properties, mainly in the generation of superficial plasmons.