Probing Conformational Heterogeneity at the Ionic Liquid-Vacuum Interface by Reactive-Atom Scattering.

Area of Science:

• Physical Chemistry
• Surface Science
• Materials Science

Background:

• Describing liquid interfaces at the atomic level is challenging due to experimental limitations.
• Existing techniques struggle to resolve molecular structure in dynamic interfacial layers.

Purpose of the Study:

• To develop a more detailed experimental method for characterizing gas-liquid interfaces.
• To investigate the molecular structure and dynamics of ionic liquids at the interface.

Main Methods:

• Utilized fluorine (F) atom scattering dynamics.
• Studied the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.
• Employed deuterium labeling for isotopic contrast.

Main Results:

• Resolved distinct signatures from cation butyl, methyl, and ring groups using HF isotopologues.
• Quantified the relative populations of cation conformations at the liquid-vacuum interface.
• Demonstrated site-specific reactivity driven by interfacial molecular organization.

Conclusions:

• F-atom scattering with isotopic labeling provides atomic-level insights into liquid interfaces.
• Molecular organization significantly influences reaction pathways at gas-liquid interfaces.
• This method advances the understanding of interfacial phenomena in ionic liquids.