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

Temperature-programmed reaction/desorption, reflection−absorption infrared spectroscopy, and density functional 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. On Cu(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−Cl bonds approximately parallel to the surface. On O/Cu(100), the gauche conformer is the predominant species and 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 an interesting contrast. The thermal stability only appears at a coverag...