Publication: Interacción de electrones secundarios y radicales con moléculas de interés biológico
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2016-02-12
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Universidad Complutense de Madrid
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Abstract
En la presente tesis se han investigado las interacciones de electrones de baja energía (10-10000 eV) con varios tipos de moléculas de interés biológico. Se han medido las secciones eficaces totales de dispersión y los espectros de pérdida de energía por medio de diferentes aparatos, con errores experimentales inferiores al 5 %. Además, se han calculado de forma teórica las secciones eficaces diferenciales e integrales mediante un método de potencial óptico basado en un modelo de átomos independientes, teniendo en cuenta los efectos de apantallamiento en el caso de blancos moleculares. Se ha comprobado la exactitud de estos cálculos comparándolos con los valores medidos para las secciones eficaces totales de dispersión de electrones, obtenidos mediante nuestros experimentos de transmisión de haz. Se han estudiado los siguientes blancos de dispersión en el margen de energías de interés: hidrógeno molecular, agua, metano, tetrahidrofurano, pirimidina y pirazina. También se presenta el conjunto de resultados preliminares correspondiente a las interacciones de radicales iónicos con moléculas de nitrometano, obtenidas con un nuevo montaje experimental basado en la medida de tiempos de vuelo (TOF). El presente estudio se centra principalmente en las medidas y la interpretación de los resultados. Los datos experimentales se han adquirido y analizado mediante un sistema automatizado de adquisición de datos desarrollado con LabVIEW, un lenguaje de programación gráfica. Después de una comparación crítica con las fuentes experimentales y teóricas disponibles, se ha elaborado un conjunto de datos colisionales de electrones autoconsistente para las moléculas anteriormente mencionadas. La base de datos colisionales generada constituye una valiosa herramienta, ya que proporciona los parámetros de entrada para los métodos de simulación Monte Carlo desarrollados para describir la interacción de la radiación a nivel molecular. Estos códigos de simulación pueden ser de gran utilidad en aquellas aplicaciones biológicas y médicas que requieren modelos de deposición de energía a nivel microscópico.
In this thesis, we have investigated low-energy electron and ion radical interactions (10–10000 eV) with some molecules of biological interest. Total scattering cross sections and energy loss spectra were measured by using different apparatus, with experimental errors within 5 %. Moreover, theoretical differential and integral cross sections have been calculated with an optical potential method based on an independent atom model, taking into account screening effects for molecular targets. The accuracy of these calculations has been checked by comparison with total electron scattering cross section data we have measured in our transmission beam experiments. The scattering targets studied in the energy range of interest are molecular hydrogen, water, methane, tetrahydrofuran, pyrimidine and pyrazine. We also present the preliminary set of results corresponding to ion radical interactions with nitromethane molecules, obtained with a novel experimental setup based on time-of-flight (TOF) measurements. The main focus of this study lies on the measurements and the interpretation of the results. Experimental data were taken and analyzed with an automatic dataacquisition system developed with LabVIEW, a graphical programming language. After a critical comparison with the available experimental and theoretical sources, self-consistent electron collisional data sets are recommended for the aforementioned molecules. The collisional database generated is a valuable tool, as it provides input data for Monte Carlo simulation methods which have been developed to describe radiation interaction at the molecular level. These simulation codes can be very useful in biological and medical applications when microscopic energy deposition models are required.
In this thesis, we have investigated low-energy electron and ion radical interactions (10–10000 eV) with some molecules of biological interest. Total scattering cross sections and energy loss spectra were measured by using different apparatus, with experimental errors within 5 %. Moreover, theoretical differential and integral cross sections have been calculated with an optical potential method based on an independent atom model, taking into account screening effects for molecular targets. The accuracy of these calculations has been checked by comparison with total electron scattering cross section data we have measured in our transmission beam experiments. The scattering targets studied in the energy range of interest are molecular hydrogen, water, methane, tetrahydrofuran, pyrimidine and pyrazine. We also present the preliminary set of results corresponding to ion radical interactions with nitromethane molecules, obtained with a novel experimental setup based on time-of-flight (TOF) measurements. The main focus of this study lies on the measurements and the interpretation of the results. Experimental data were taken and analyzed with an automatic dataacquisition system developed with LabVIEW, a graphical programming language. After a critical comparison with the available experimental and theoretical sources, self-consistent electron collisional data sets are recommended for the aforementioned molecules. The collisional database generated is a valuable tool, as it provides input data for Monte Carlo simulation methods which have been developed to describe radiation interaction at the molecular level. These simulation codes can be very useful in biological and medical applications when microscopic energy deposition models are required.
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Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física Atómica, Molecular y Nuclear, leída el 09-12-2015