Approaching the forbidden fruit of reaction dynamics: Aiming reagent at selected impact parameters.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 30310869.
- Also identified by DOI 10.1126/sciadv.aau2821 and PMC identifier 6173530.
- Licence recorded as CC BY-NC.
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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 (CF<sub>2</sub>), 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.