title: How adsorbate alignment leads to selective reaction.
abstract: There has been much interest in the effect of adsorbate alignment in a surface reaction. Here we show its significance for an electron-induced reaction occurring along preferred axes of the asymmetric Cu(110) surface, characterized by directional copper rows. By scanning tunneling microscopy (STM), we found that the heterocyclic aromatic reagent, physisorbed meta-iodopyridine, lay with its carbon-iodine either along the rows of Cu(110), "A", or perpendicular, "P". Electron-induced dissociative attachment with the C-I bond initially along "A" gave a chemisorbed I atom and chemisorbed vertical pyridyl, singly surface-bound, whereas that with C-I along "P" gave a chemisorbed I atom and a horizontal pyridyl, doubly bound. An impulsive two-state model, involving a short-lived antibonding state of C-I, accounted for the different product surface binding in terms of closer Cu···Cu atomic spacing along "A" accommodating only one binding site of the pyridyl ring recoiling from I and wider spacing along "P" accommodating simultaneously both binding sites, N-Cu and C-Cu, in the meta-position on the recoiling pyridyl ring. STM studies combined with dynamical modeling can be seen as a way to improve understanding of the role of surface alignment in determining reactive outcomes in induced reaction at asymmetric crystalline surfaces.
authors.affiliation: Lash Miller Chemical Laboratories, Department of Chemistry and Institute of Optical Sciences, University of Toronto , Toronto, Ontario M5S 3H6, Canada .
authors.forename: Fang
authors.initials: F
authors.lastname: Cheng
authors.forename: Wei
authors.initials: W
authors.lastname: Ji
authors.forename: Lydie
authors.initials: L
authors.lastname: Leung
authors.forename: Zhanyu
authors.initials: Z
authors.lastname: Ning
authors.forename: John C
authors.initials: JC
authors.lastname: Polanyi
authors.forename: Chen-Guang
authors.initials: CG
authors.lastname: Wang