Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 8: Metal Substrates I: Adsorption and Reactivity

O 8.7: Vortrag

Montag, 1. April 2019, 12:00–12:15, H25

Colliding Molecules at Selected Impact Parameters — •Kelvin Anggara, Lydie Leung, Matthew Timm, Zhixin Hu, and John Polanyi — Department of Chemistry and Institute of Optical Sciences, University of Toronto, 80 St. George Street, Toronto M5S 3H6, Canada

The dynamics for bimolecular reaction has been elucidated by crossing two molecular beams in the gas-phase under single-collision conditions. The results however have inevitably been averaged over impact parameters - the collision ’miss-distance’ - ranging from zero to infinity, obscuring the effect of this important parameter on reaction dynamics. We show that this averaging can be avoided by a aiming a highly-collimated ’projectile’ molecule towards a fixed ’target’ molecule, with both adsorbed at a surface. Using an electron from the tip of a Scanning Tunnelling Microscope (STM), a single chemisorbed CF₃ on Cu(110) at 4.6 K can be reacted to give a recoiling CF₂ radical that is collimated to a lateral spread of only ±1^∘. Previous work from this lab has shown that this collimation effect is due to the interaction of the CF₂ with the underlying Cu-row which acts as an atomic guide to give a directed CF₂ ’surface-molecular-beam’. Here we have aimed the CF₂ beam at a chemisorbed vinyl (CHCH₂) with three impact parameters (-4.0, -0.4, and +3.2 Å), giving insights into the dynamics of carbon chain growth on the metal surface. The scattering experiment presented here has the potential to be aimed at any target that can be detected by STM on a surface, thereby providing a means to explore the dynamics in a wide range of surface reactions.