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Doctoral Thesis
DOI
10.11606/T.76.1995.tde-06042015-150522
Document
Author
Full name
Otil Lara
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1995
Supervisor
Committee
Machado, Luiz Eugenio (President)
Tao, Lee Mu (President)
Lima, Marco Aurelio Pinheiro
Machado, Francisco Bolivar Correto
Trsic, Milan
Title in Portuguese
Novos métodos teóricos para estudos de espalhamento de elétrons e pósitrons envolvendo processos multicanais
Keywords in Portuguese
Não disponível
Abstract in Portuguese
Dada a relevância de efeitos multicanais na interação de elétrons de baixa energia com átomos e moléculas, a consideração destes, nos cálculos de secção de choque, se torna indispensável. O objetivo do presente trabalho visa encontrar um método teórico aplicável aos espalhamentos multicanal de elétrons por moléculas, que deve reunir qualidades, tais como a exatidão de resultados calculados e a eficiência computacional. Foram propostos dois novos formalismos teóricos, que são, respectivamente, o Método de "Two-Potential" Multicanal e o Método do Funcional-C Multicanal. Estes dois métodos foram desenvolvidos com base no Método de Ondas Distorcidas e no Princípio Variacional de Schwinger. Por outro lado, um método iterativo, conhecido como Método das Frações Contínuas, proposto por Horacek e Sasakawa, em 1983, foi também adaptado, pela primeira vez, para espalhamentos multicanais. Estes três novos métodos foram testados para resolver problemas de espalhamento multicanais com o modelo de potencial de Huck, e também para o espalhamento de pósitron por átomos de hidrogênio, ao nível de dois e de cinco canais. Nossos resultados mostraram que, entre estes três métodos, o de Frações Contínuas apresenta o melhor desempenho, tanto na eficiência computacional, quanto na exatidão dos resultados obtidos. Nosso estudo indica o grande potencial do Método de Frações Contínuas para o estudo de espalhamento de elétrons por moléculas. A generalização deste método para cálculos realísticos está em andamento
Title in English
Not available
Keywords in English
Not available
Abstract in English
It is well known that mutichannel effects strongly influence the low-energy electron scattering by atoms and molecules. Nevertheless, the inclusion of such effects in the calculations of scattering cross sections remains a considerable task for the researches of the area due to the complexity of the problem. In the present study, we aim to develop a new theoretical method which can be efficiently applied to the multichannel scattering studies. Two new theoretical formalism, namely, the multichannel two-potential method and the multichannel c-fucntional method have been proposed. Both methods were developed on the base of well known Distorted- Wave Method combined with Schwinger Variational Principle. In addition, an interative method proposed by Horaceck and Sasakawa in 1983, the Method of continued fractions, is adapted by the first time to multichannel scatterings. Numerical test of these three methods were carried out through applications to solve the multichannel scattering problems envolving the interaction of an electron with Huck model potential as well as to treat the positron scattering by atomic hydrogen in the two-channel-coupling and five-channel-coupling levels. The results of these applications show that the Method of continued fractions is computationally the most efficient and can provide exact cross sections within the numerical precision of the method. Thus, the present study indicates the potential of this method and some realistic studies of electron-molecule scattering using the Method of continued fractions are now in progress
 
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Publishing Date
2015-04-07
 
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