The mutual neutralization of hydronium and hydroxide

Area of Science:

• Physical Chemistry
• Chemical Physics
• Ion Chemistry

Background:

• Mutual neutralization of hydronium (H3O+) and hydroxide (OH-) ions is a fundamental reaction.
• Limited experimental data exists on the specific reaction mechanisms involved.

Purpose of the Study:

• To investigate the reaction mechanisms of mutual neutralization for cold, isolated hydronium and hydroxide ions.
• To provide experimental benchmarks for theoretical models of charge-transfer mechanisms.

Main Methods:

• Utilizing three-dimensional imaging of coincident neutral products.
• Employing the cryogenic double electrostatic ion-beam storage ring (DESIREE) for low-energy ion collisions.
• Analyzing product channels and internal energy distributions.

Main Results:

• Identified predominant H2O + OH + H and 2OH + H2 product channels, attributed to electron transfer.
• Observed a minor H2O + H2O channel with high internal excitation, attributed to proton transfer.
• Measured mechanism-resolved internal product excitation and dependence on collision energy and ion temperature.

Conclusions:

• The study elucidates the dominant electron-transfer mechanism in mutual neutralization.
• Provides crucial experimental data for validating theoretical models of ion-molecule reactions.
• Highlights the importance of low-energy collision studies for understanding fundamental chemical processes.