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Habilitation Thesis
DOI
10.11606/T.54.2011.tde-08082011-115418
Document
Author
Full name
Luiz Nunes de Oliveira
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1984
Committee
Koberle, Roland (President)
Fóglio, Mário Eusébio
Leite, Jose Roberto
Missell, Frank Patrick
Tsu, Raphel
Title in Portuguese
Modelo e cálculo do tempo de relaxação vibracional de moléculas adsorvidas quimicamente em superfícies metálicas
Keywords in Portuguese
Adsorção química
Tempo de relaxação
Abstract in Portuguese
Mostra-se que o modelo de Anderson-Newns para adsorção química em superfícies metálicas transgride a regra de soma de Friedel. Para garantir que o sistema seja eletricamente neutro, introduz-se urna repulsão G entre os elétrons de condução e a carga transferida para o adsorvido. O Hamiltoniano de muitos corpos resultante se diagonaliza por um procedimento numérico fundamentado na teoria do grupo de renormalização. Para mostrar que o potencial G influencia a interpretação de resultados experimentais, aplica-se o modelo ao sistema carbono-hidrogênio no óxido de metila (CH3OH-) adsorvido em Cu (100), cujo espectro vibracional foi recentemente medido. Comparando as frequências vibracionais desse sistema com as do metanol (CH3OH) gasoso, estabelece-se um limite superior Vmax para o acoplamento Ventre estados de Bloch e orbitais moleculares da ligação C-H. Para Vmax, ao arrepio dos resultados para G=O, o modelo generalizado prevê larguras de linha de absorção que concordam com os dados experimentais.
Title in English
Relaxation time for molecules chemically adsorved on metallic surfaces
Keywords in English
Chemsorption
Relaxation time
X-ray absorption
Abstract in English
It is shown that the Anderson-Newns model for chemisorption on metallic surfaces violates the Friedel sum rule; to ensure electrical neutrality, a repuls10n G between the conduction electrons and the charge transferred to the adsorbate is introduced. A renormalization group procedure diagonalizes the resulting many-body Hamiltonian. The model is applied to the carbon-hydrogen system in methoxide (CH3OH-) chemisorbed on Cu (100), the infrared absorption spectrum of which was recently measured. On the basis of a comparison with the vibrational frequencies in methanol (CH3OH) gas, an upper bound Vmax for the coupling V between Bloch states and C-H molecular orbitals is established. For Vmax, in contrast with the (Anderson-Newns) G=O case, the absorption linewidths calculated for the generalized model agree well with the experimental results.
 
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Publishing Date
2011-08-19
 
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