Differential and integral cross sections in OH(X) + Xe collisions

Area of Science:

• Chemical Physics
• Molecular Collisions
• Quantum Scattering

Background:

• Hydroxyl radical (OH) is a key species in atmospheric and combustion chemistry.
• Understanding OH collisions is crucial for modeling reactive systems.
• Previous studies lacked detailed state-resolved collision data.

Purpose of the Study:

• To experimentally measure differential cross sections (DCSs) for inelastic OH(X) + Xe collisions.
• To compare experimental data with theoretical calculations using ab initio potential energy surfaces (PES).
• To investigate the influence of reduced mass on scattering dynamics by comparing with OH + He.

Main Methods:

• State-selected OH radicals prepared using hexapole electric field selection.
• Product state detection via [2 + 1] resonance-enhanced multiphoton ionization and velocity-map imaging.
• Integral cross sections measured by laser-induced fluorescence.
• Comparison with exact close-coupling quantum mechanical scattering calculations.

Main Results:

• Experimental DCSs for OH(X) + Xe collisions at 483 cm⁻¹ were obtained.
• Good agreement observed between experimental and theoretical DCSs, validating the PES.
• Discrepancies noted at low scattering angles warrant further investigation.
• Theoretical DCSs for OH(X) + He were computed and compared to OH(X) + Xe.

Conclusions:

• Experimental measurements provide a benchmark for testing theoretical PESs of open-shell systems.
• The study highlights the capability of state-resolved collision experiments in refining theoretical models.
• Reduced mass significantly influences DCSs and partial cross sections in OH collisions.