Low-lying Negative Ion States Probed in Potassium - Ethanol Collisions

Area of Science:

• Physical Chemistry
• Chemical Physics
• Atomic and Molecular Collisions

Background:

• Dissociative electron transfer (DET) is a fundamental process in chemical reactions.
• Understanding negative ion formation pathways is crucial for chemical dynamics.
• Ethanol is a common molecule with diverse chemical properties.

Purpose of the Study:

• To investigate the dissociative electron transfer in collisions between potassium atoms and ethanol molecules.
• To identify the primary negative ions formed and their fragmentation channels.
• To explore the role of the electron donor in influencing reaction pathways.

Main Methods:

• Time-of-flight mass spectrometry was used to analyze negative ion products.
• Collision energies ranged from 17.5 to 350 eV in the lab frame.
• Potassium cation energy loss spectra were recorded to study electronic states.
• Quantum chemical calculations were performed to support experimental findings.

Main Results:

• Hydroxyl anion (OH⁻) was the dominant product, followed by C₂H₅O⁻, O⁻, CH₃⁻, and CH₂⁻.
• Branching ratios exhibited significant energy dependence at low to intermediate collision energies.
• A Feshbach resonance at 9.36±0.10 eV and a shape resonance at 3.16±0.10 eV were identified.
• The hydroxyl anion channel was dominant, contrasting with findings from dissociative electron attachment experiments.

Conclusions:

• The electron donor's proximity significantly influences temporary negative ion formation and reaction pathways.
• DET reactions can access channels not observed in dissociative electron attachment.
• The study provides insights into the electronic structure and dynamics of negative ions formed during K + ethanol collisions.