Journal of Physical Chemistry B, Vol.105, No.43, 10600-10609, 2001
1-chloro-2-fluoroethane adsorption on Cu(111): Structure and bonding
The adsorption of 1-chloro-2-fluoroethane on Cu(111) has been studied using low-energy electron diffraction, Auger electron spectroscopy, UV photoelectron spectroscopy, line of sight temperature-prognunmed desorption, and normal incidence X-ray standing wave (NIXSW) analysis. The molecule adsorbs and desorbs molecularly. The activation energy for desorption of the first layer increases linearly from 30.8 to 32.8 kJ mol(-1) as the coverage increases from zero to full monolayer coverage with a preexponential of 10(12) s(-1). The activation energy for the multilayer is found to be 27.1 kJ mol(-1) for the same preexponential value. The NIXSW structural tudy shows that the molecule bonds via its chlorine end, in an atop site, with a Cu . . . Cl distance of 3.06 +/- 0.06 Angstrom. The fluorine end, at a distance of 3.02 +/- 0.1 A from the surface copper plane, is also located approximately in an atop site. This orientates the molecule with its Cl . . .F axis parallel to the surface. These results are compared with similar ones for 1,2-dichloroethane and 1-bromo-2-chloroethane on Cu(111). All three molecules have similar adsorption geometries, bonding via a single halogen (the heaviest) in an atop site, while the bond strength is determined, predominantly, by this halogen.