AVS 46th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS2-TuM

Paper SS2-TuM8
Increasing the C-O Bond Anharmonicity of Methoxy on Cu(100) with Coadsorbates

Tuesday, October 26, 1999, 10:40 am, Room 607

Session: Model Catalysts
Presenter: H. Ihm, University of Texas, Austin
Authors: J.M. White, University of Texas, Austin
H. Ihm, University of Texas, Austin
K.C. Smith, University of Texas, Austin
H. Celio, University of Texas, Austin
Correspondent: Click to Email
The C-O bond ahnarmonicity of methoxy induced by coadsorbates on Cu(100) has been studied using reflection absorption infrared spectroscopy (RAIRS). The analysis of the anharmonicity was carried out through the IR spectrum of a localized two-phonon bound state, the 2@nu@'@sub C-O@ excitation. For methoxy without coadsorbates, the vibrational frequencies of the C-O stretching mode and its overtone exhibit large coverage dependent shifts caused by dipole-dipole interactions. The anharmonicity of the C-O bond is @omega@@sub e@@chi@@sub e@=8.5 cm@sup -1@, which is 34% lower than that found for the gas phase methanol. Atomic oxygen markedly shifts the 2@nu@'@sub C-O@ band from 1951 cm@sup -1@ to 1940 cm@sup -1@, which consequently increases the anharmonicity by 11 cm@sup -1@. We have also compared results for methoxy from the thermal decomposition of methyl nitrite (CH@sub 3@ONO) on Cu(100) at different temperatures. We find that the 2@nu@'@sub C-O@ band can detect the presence of coadsorbed NO since the vibrational properties of the 2@nu@'@sub C-O@ band for both systems (methoxy-A-Cu(100) where A=O or NO) are quite similar. The definite correlation of the changes to the vibrational properties of methoxy induced by coadsorbates was achieved by using temperature programmed desorption (TPD) and Auger electron spectroscopy (AES).