Decoding the spectroscopic features and time scales of aqueous proton defects

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Spectroscopy

Background:

• Acid solutions feature complex proton defect structures and dynamics.
• Disentangling proton defect structures and interconversion mechanisms in water is challenging.

Purpose of the Study:

• To elucidate the transient structural motifs and interconversion mechanisms of proton defects in aqueous environments.
• To connect experimental spectroscopic features and relaxation timescales with molecular dynamics.

Main Methods:

• Quantum simulations treating electrons and nuclei.
• Development and application of a physically transparent coordinate for proton defect solvation asymmetry.

Main Results:

• A novel coordinate successfully explains features in linear vibrational spectra.
• This coordinate elucidates molecular motions responsible for interconversion timescales in nonlinear experiments.
• The study provides a unified condensed-phase picture of proton structure and dynamics.

Conclusions:

• The developed coordinate unifies the understanding of proton defects in liquid phases.
• The findings encompass proton sharing and resemble gas-phase Eigen and Zundel structures.
• This work offers insights into the dynamic nature of protons in aqueous solutions.