title: Interactions of D2O with methane and fluoromethane surfaces.
abstract: TOF-SIMS is used to investigate the interactions between D2O and hydrophobic molecules, such as CH4, CH3F, CH2F2, CHF3, and CF4, at cryogenic temperatures (15 K). By irradiation with a 1.5-keV He+ beam, the D(+)(D2O)n ions are ejected efficiently from the D2O nanoclusters physisorbed on the CF4 layer due to Coulomb explosion: the ion yields are by about two orders of magnitude higher than those from a thick D2O layer via the kinetic sputtering. The D(+)(D2O)n yields decrease on the CHnF(4-n) layer with increasing the number of the C-H group. This is because the Coulombic fission is quenched due to the delocalization of valence holes through the C-H...H-C and C-H...D2O contacts. A pure D2O film is hardly grown on the CH4 layer as a consequence of intermixing whereas the D2O molecules basically adsorb on the surfaces of fluoromethanes, suggesting the attractive (water-repellent) interactions in the C-H...D2O (C-F...D2O) contacts. The C-H...O bond behaves like a conventional O-H...O hydrogen bond as far as the collision-induced proton transfer reaction is concerned.
authors.affiliation: Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan. souda.Ryutaro@nims.go.jp
authors.forename: R
authors.initials: R
authors.lastname: Souda
authors.forename: H
authors.initials: H
authors.lastname: Kawanowa
authors.forename: M
authors.initials: M
authors.lastname: Kondo
authors.forename: Y
authors.initials: Y
authors.lastname: Gotoh