Pressure Effects on Water Dynamics by Time-Resolved Optical Kerr Effect.

Area of Science:

• Physical Chemistry
• Thermodynamics
• Materials Science

Background:

• Water exhibits unusual thermodynamic and dynamic properties in its liquid and supercooled states.
• The exact nature of these liquid phases remains a subject of scientific debate.

Purpose of the Study:

• To investigate the thermodynamic and dynamical anomalies of water under varying pressure conditions.
• To explore the behavior of water in its supercooled metastable phase.

Main Methods:

• Utilized the optical Kerr effect to measure water properties.
• Conducted experiments at two isotherms (273 K and 297 K) across a wide pressure range (0.1 to 1350 MPa).

Main Results:

• Observed peculiar pressure dependencies in structural relaxation and low-frequency vibrational dynamics.
• Data suggests a crossover area in the water phase diagram.
• Identified two distinct dynamic regimes related to high-density and low-density water forms.

Conclusions:

• The study provides evidence for two distinct dynamic regimes in liquid water.
• These regimes are linked to different forms of water (high-density and low-density).
• A crossover area in the phase diagram separates these dynamic behaviors.