Vibrational excitation induces double reaction

Area of Science:

• Surface science
• Physical chemistry
• Materials science

Background:

• Electron-induced reactions on metal surfaces are crucial for catalysis and materials modification.
• Previous studies focused on electronic excitation near the threshold (1.0 eV).
• Understanding reaction dynamics at lower energies is essential for controlling surface processes.

Purpose of the Study:

• To compare vibrational and electronic excitation pathways for electron-induced reactions.
• To investigate reaction dynamics at electron energies below the electronic excitation threshold.
• To elucidate the role of vibrational modes in dissociating molecules on metal surfaces.

Main Methods:

• Utilizing scanning tunneling microscopy (STM) to probe reaction dynamics.
• Comparing electron-induced reactions at 0.3 eV (vibrational) versus 1.0 eV (electronic excitation).
• Employing ab initio calculations to model vibrational excitation of C-I bonds.

Main Results:

• Vibrational excitation at 0.3 eV resulted in a fourth-order rate dependence on current, indicating multistep vibrational excitation.
• Electronic excitation at 1.0 eV showed a first-order rate dependence.
• Altered reaction dynamics and product binding patterns were observed with vibrational excitation.
• Modeling vibrational excitation of C-I bonds reproduced the observed changes in reaction dynamics.

Conclusions:

• Vibrational excitation offers a distinct pathway for controlling electron-induced surface reactions compared to electronic excitation.
• Multistep vibrational excitation plays a significant role at low electron energies.
• Understanding these excitation mechanisms provides insights into selective bond activation on metal surfaces.