Sci. Adv. 4: 2821 (2018)
Approaching the forbidden fruit of reaction dynamics: Aiming reagent at selected impact parameters
Anggara, Kelvin1,2, Leung, Lydie1,2, Timm, Matthew J.1,2, Hu, Zhixin1,2,3,4, Polanyi, John C.1,2,*
1. Univ Toronto, Dept Chem, Lash Miller Chem Labs, 80 St George St, Toronto, ON M5S 3H6, Canada
2. Univ Toronto, Inst Opt Sci, 80 St George St, Toronto, ON M5S 3H6, Canada
3. Tianjin Univ, Ctr Joint Quantum Studies, Tianjin 300350, Peoples R China
4. Tianjin Univ, Dept Phys Tianjin Univ, Tianjin 300350, Peoples R China
* Corresponding Authors: John C. Polanyi ( jpolanyi@chem.utoronto.ca )
Abstract
Collision geometry is central to reaction dynamics. An important variable in collision geometry is the miss-distance between molecules, known as the “impact parameter.” This is averaged in gas-phase molecular beam studies. By aligning molecules on a surface prior to electron-induced dissociation, we select impact parameters in subsequent inelastic collisions. Surface-collimated “projectile” molecules, difluorocarbene (CF2), were aimed at stationary “target” molecules characterized by scanning tunneling microscopy (STM), with the observed scattering interpreted by computational molecular dynamics. Selection of impact parameters showed that head-on collisions favored bimolecular reaction, whereas glancing collisions led only to momentum transfer. These collimated projectiles could be aimed at the wide variety of adsorbed targets identifiable by STM, with the selected impact parameter assisting in the identification of the collision geometry required for reaction.
