1,2-Dichloroethane on Cu(100) and Oxygen-Covered Cu(100): Conformation, Orientation, and Transformation

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• 作者：Kuan-Huang Kuo ; Yi-Shiue Lin ; Jain-Jung Shih ; Yung-Hsuan Liao ; Jian-Shiun Lin ; Che-Ming Yang ; Jong-Liang Lin
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：May 31, 2007
• 年：2007
• 卷：111
• 期：21
• 页码：7757 - 7764
• 全文大小：332K
• 年卷期：v.111,no.21(May 31, 2007)
• ISSN：1932-7455

文摘

Temperature-programmed reaction/desorption, reflection-absorption infrared spectroscopy, and densityfunctional theory calculations have been employed to investigate the adsorption of ClCH₂CH₂Cl on Cu(100)and O/Cu(100) in the subjects of identification of the rotational isomers, adsorption energy, adsorption geometry,thermal stability of the layer structure, and transformation between the trans and gauche conformers. OnCu(100), both the trans and gauche forms of ClCH₂CH₂Cl coexist on the surface at a monolayer coverage,and their thermal desorption peak appears at 187 K. The trans molecules are likely adsorbed with the C-Clbonds approximately parallel to the surface. On O/Cu(100), the gauche conformer is the predominant speciesand the desorption temperature is shifted to 199 K. It is found that the ClCH₂CH₂Cl layer structure on Cu(100),up to a ~15 monolayer coverage studied, is stable between 120~140 K. However, O/Cu(100) shows aninteresting contrast. The thermal stability only appears at a coverage below ~3 monolayers. The transformationfrom gauche to trans takes place for higher coverages. On the basis of the cluster-model calculations withoutconsideration of the interaction between adsorbed molecules, it is shown that the activation energy for thetransformation between trans and gauche ClCH₂CH₂Cl on O/Cu(100) is much lower than that on Cu(100),suggesting that the trans molecules are easier to be transformed into gauche ones on O/Cu(100), as they areadsorbed on the proximity of preadsorbed oxygen atoms.