Publication: Estudio de la fotodisociación y fotoionización de radicales libres por imágenes de iones y fotoelectrones
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2021-01-20
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Universidad Complutense de Madrid
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Abstract
"Introducción"Los radicales libres están presentes en un gran número de procesos como intermediarios en reacciones en la química atmosférica, interestelar e incluso la combustión de hidrocarburos. Los radicales alquílicos más sencillos, como el radical metilo y el etilo, son considerados prototipos para estudios teóricos y experimentales. A su vez, los radicales libres halogenados son de vital importancia como fuente de halógenos en la atmósfera, convirtiéndose en precursores de la formación de aerosoles o partículas, e incluso de otros compuestos de gran interés, como los intermedios de Criegee, que mejoran la capacidad oxidante de la atmósfera favoreciendo así la formación de aerosoles orgánicos secundarios. Por tanto, tiene un gran interés conocer la dinámica de fotodisociación y fotoionización de estos radicales.En esta Tesis Doctoral se investiga la dinámica de fotodisociación de diversos radicales alquílicos mediante técnicas de cartografía de velocidades con imágenes de iones en combinación con láseres pulsados de nanosegundos, así como la dinámica de fotoionización de radicales e intermedios de Criegee mediante la detección de fotoiones y fotoelectrones en coincidencias empleando radiación sincrotrón."Objetivos"Los principales objetivos de esta Tesis Doctoral son: comprender las vías de fotodisociación de los dos radicales alquílicos más simples, el radical metilo (CH3) y el radical etilo (C2H5), esclareciendo los distintos mecanismos de reacción gracias a la ayuda de cálculos ab initio de estructura electrónica de estados excitados de alto nivel; y estudiar la dinámica de fotoionización de los radicales CHnI (n=0-2) y del intermedio de Criegee CH2OO, para poder determinar, en particular, las energías de ionización adiabáticas, vitales para poder comprender procesos químicos en los que están involucrados los respectivos iones...
"Introduction" Free radicals are present in a large number of processes as intermediates in reactions in atmospheric and interstellar chemistry and even hydrocarbon combustion. The simplest alkyl radicals, such as methyl and ethyl radicals, are considered as prototypes for theoretical and experimental studies. Moreover, halogenated free radicals are of great importance as a source of halogens for the atmosphere, becoming precursors for the formation of aerosols or particles and even other compounds of great interest, such us Criegee intermediates, wich improve the oxidizing capacity of the atmosphere thus favoring the formation of secondary organic aerosols. Hence, it is of great interest to know the dynamics of photodissociation and photoionization of these radicals.The photodissociation dynamics of various alkyl radicals have been investigated in this Ph.D. Thesis by means of velocity map imaging techniques in combination with pulsed nanosecond lasers, as well as the photoionization of radicals and Criegee intermidietes by means of the photoelectron photoion coincidence technique using syncrotron radiation."Objectives"The main objectives of this Ph.D. Thesis are: understanding the photodissociation pathways of the two simplest alkyl radicals, the methyl radical (CH3) and the ethyl radical (C2H5), clarifying the di_erent reaction mechanisms with the support of high level ab initio calculations of electronic structure of excited states; and study the ionization dynamics of CHnI (n=0-2) radicals and the simplest Criegee intermediate (CH2OO), in order to determine, in particular, the adiabatic ionization energies, vital to understand chemical processes where these ions are involved...
"Introduction" Free radicals are present in a large number of processes as intermediates in reactions in atmospheric and interstellar chemistry and even hydrocarbon combustion. The simplest alkyl radicals, such as methyl and ethyl radicals, are considered as prototypes for theoretical and experimental studies. Moreover, halogenated free radicals are of great importance as a source of halogens for the atmosphere, becoming precursors for the formation of aerosols or particles and even other compounds of great interest, such us Criegee intermediates, wich improve the oxidizing capacity of the atmosphere thus favoring the formation of secondary organic aerosols. Hence, it is of great interest to know the dynamics of photodissociation and photoionization of these radicals.The photodissociation dynamics of various alkyl radicals have been investigated in this Ph.D. Thesis by means of velocity map imaging techniques in combination with pulsed nanosecond lasers, as well as the photoionization of radicals and Criegee intermidietes by means of the photoelectron photoion coincidence technique using syncrotron radiation."Objectives"The main objectives of this Ph.D. Thesis are: understanding the photodissociation pathways of the two simplest alkyl radicals, the methyl radical (CH3) and the ethyl radical (C2H5), clarifying the di_erent reaction mechanisms with the support of high level ab initio calculations of electronic structure of excited states; and study the ionization dynamics of CHnI (n=0-2) radicals and the simplest Criegee intermediate (CH2OO), in order to determine, in particular, the adiabatic ionization energies, vital to understand chemical processes where these ions are involved...
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Tesis inédita de la Universidad Complutense de Madrid. Facultad de Ciencias Químicas, leída el 29-04-2020