Spin-dependent reactivity and spin-flipping dynamics in oxygen atom scattering from graphite

Area of Science:

• Surface Chemistry
• Chemical Physics
• Heterogeneous Catalysis

Background:

• Two-electron chemical bond formation necessitates spin alignment, influencing gas-phase reaction kinetics.
• The role of electronic spin in surface chemistry and heterogeneous catalysis remains debated due to a lack of definitive state-to-state experimental data.

Purpose of the Study:

• To investigate the influence of initial electronic spin states on the reactivity of oxygen atoms with a graphite surface.
• To determine the spin conservation or non-conservation during surface reactions.
• To elucidate the mechanistic pathways governing oxygen-graphite interactions.

Main Methods:

• Utilized an incoming/outgoing correlation ion imaging technique for scattering experiments involving O(3P) and O(1D) atoms with graphite.
• Controlled the initial spin-state distribution of incident oxygen atoms.
• Determined the final spin states of departing oxygen atoms.
• Performed molecular dynamics simulations on machine-learning-assisted first-principles potential energy surfaces.

Main Results:

• Demonstrated that oxygen atoms in the O(1D) electronic state exhibit higher reactivity towards graphite compared to the O(3P) state.
• Identified electronically non-adiabatic pathways where incident O(1D) atoms are quenched to the O(3P) state before departing the surface.
• Molecular dynamics simulations confirmed that spin-forbidden transitions occur, albeit with low probabilities.

Conclusions:

• The electronic spin state significantly impacts the reactivity of oxygen atoms on a graphite surface.
• Non-adiabatic processes play a role in oxygen-surface interactions, allowing for spin state changes.
• This work provides crucial mechanistic insights into spin dynamics in surface chemistry, relevant for catalysis.