The adsorption of benzene and naphthalene on the Rh(111) surface: A LEED,AES and TDS study |
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Authors: | RF Lin RJ Koestner MA Van Hove GA Somorjai |
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Institution: | Materials and Molecular Research Division, Lawrence Berkeley Laboratory and Department of Chemistry, University of California, Berkeley, California 94720, USA |
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Abstract: | The adsorption of benzene and naphthalene on the Rh(111) single-crystal surface has been studied by low-energy electron diffraction (LEED), Auger electron spectroscopy (AES) and thermal desorption spectroscopy (TDS). Both benzene and naphthalene form two different ordered surface structures separated by temperature-induced phase transitions: benzene transforms from a () structure, which can also be labelled c()rect, to a (3 × 3) structure in the range of 363–395 K, while naphthalene transforms from a ()R30° structure to a (3 × 3) structure in the range 398–423 K. Increasing the temperature further, these structures are found to disorder at about 393 K for benzene and about 448 K for naphthalene. Then, a first H2 desorption peak appears at about 413 K for benzene and 578 K for naphthalene and is interpreted as due to the occurrence of molecular dissociation. All these phase transitions are irreversible. The ordered structures are interpreted as due to flat-lying or nearly flat-lying intact molecules on the rhodium surface, and they are compared with similar structures found on other metal surfaces. Structural models and phase transition mechanisms are proposed. |
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