Direct and Delayed Dynamics in Electron-Induced Surface Reaction

Area of Science:

• Surface science
• Physical chemistry
• Materials science

Background:

• Understanding electron-induced reactions is crucial for surface chemistry.
• Vinyl bromide and allyl bromide are key molecules in organic synthesis and materials science.

Purpose of the Study:

• To investigate the electron-induced reaction pathways of vinyl bromide and allyl bromide on a Cu(110) surface.
• To elucidate the dynamics and mechanisms of these surface reactions.

Main Methods:

• Experimental study using scanning tunneling microscopy (STM) at 4.6 K.
• Theoretical investigation using molecular dynamics (MD) simulations.

Main Results:

• Two reaction pathways were identified: "Direct" (under the tip) and "Delayed" (spontaneous after diffusion).
• The "Delayed" pathway was a major route, accounting for 68% of vinyl bromide and 53% of allyl bromide reactions.
• Evidence for a long-lived vibrationally excited intermediate was observed for both pathways.
• MD simulations confirmed that specific vibrational modes dictate either Direct or Delayed reaction outcomes.

Conclusions:

• The study reveals a novel "Delayed" reaction pathway for electron-induced reactions of vinyl and allyl bromide on Cu(110).
• Vibrational excitation plays a critical role in determining the reaction dynamics and outcomes.