Slow solvation dynamics beyond dielectric relaxation by three-pulse photon echo peak shift

Area of Science:

• Physical Chemistry
• Chemical Physics
• Materials Science

Background:

• Liquid dynamics and solute coupling are vital for understanding liquid-phase chemical processes.
• Solute time-correlation functions typically decay due to solvent motion in homogeneous solutions.

Purpose of the Study:

• To investigate liquid dynamics and solute coupling using advanced spectroscopy.
• To resolve dynamics across a wide timescale (femtoseconds to nanoseconds) and temperature range (80-298 K).

Main Methods:

• Utilized a diffractive optics-based three-pulse photon echo peak shift (3PEPS) apparatus.
• Employed 3PEPS, a third-order nonlinear spectroscopy technique, to measure solute time-correlation functions.
• Varied experimental conditions including temperature and probe solute molecules.

Main Results:

• Observed dynamics slower than n-alcohol dielectric relaxation, even at room temperature.
• Identified a persistent ~0.5 ns time constant and a nanosecond timescale static offset.
• Dynamics persisted below the melting points of the studied liquids.

Conclusions:

• Proposed that locally formed, glass-like clusters in liquids are responsible for the observed slow dynamics.
• Results offer new perspectives on liquid dynamics, liquid-glass transitions, and liquid-liquid phase transitions.