Coverage dependent non-adiabaticity of CO on a copper surface

Area of Science:

• Surface science
• Physical chemistry
• Femtochemistry

Background:

• Understanding electron-vibrational energy transfer is crucial for surface chemistry.
• Carbon monoxide (CO) on metal surfaces is a model system for studying adsorbate dynamics.

Purpose of the Study:

• Investigate the coverage-dependent energy transfer dynamics between hot electrons and CO on Cu(110).
• Elucidate the role of adsorbate-adsorbate interactions in controlling non-adiabatic coupling.

Main Methods:

• Utilized femtosecond visible pump, sum frequency probe spectroscopy.
• Analyzed the C-O stretch frequency transients as a function of CO coverage.

Main Results:

• Observed a coverage-dependent red shift in C-O stretch frequency transients (3 cm(-1) at 0.1 ML to 9 cm(-1) at 0.77 ML).
• Found that non-adiabatic coupling strength increases with CO coverage.
• Identified the frustrated rotational mode as the cause of non-adiabatic behavior.

Conclusions:

• Adsorbate-adsorbate repulsive interactions lead to an anharmonic potential energy surface and increased electronic density of states.
• These interactions enhance non-adiabatic coupling, providing a new pathway to control adsorbate dynamics.