Supercooled water relaxation dynamics probed with heterodyne transient grating experiments

Area of Science:

• Physical Chemistry
• Fluid Dynamics
• Dielectric Spectroscopy

Background:

• Understanding the dynamic properties of water, especially in its supercooled state, is crucial for various scientific disciplines.
• Existing models often struggle to fully capture the complex interplay of density and temperature fluctuations in water's dielectric behavior.

Purpose of the Study:

• To investigate the dynamic properties of liquid and supercooled water across a broad temperature range (-17.5 to 90 °C).
• To elucidate the influence of density and temperature fluctuations on the dielectric function of water.
• To develop and validate a hydrodynamic model for describing water's behavior in transient grating experiments.

Main Methods:

• Heterodyne-detected transient grating spectroscopy was employed over an extended time window.
• A comprehensive hydrodynamic model incorporating coupled density and temperature variables was developed.
• Laser-induced heating and electrostrictive effects were analyzed within the experimental framework.

Main Results:

• The study successfully extracted key dynamic properties: sound velocity, sound attenuation, and thermal diffusivity.
• The temperature dependence of the dielectric constant and the ratio of dielectric thermodynamic derivatives were determined.
• Experimental data clearly demonstrated the significant effects of density and temperature fluctuations on water's dielectric function.

Conclusions:

• The developed hydrodynamic model accurately describes experimental data from transient grating experiments on water.
• The findings provide critical insights into the physics of liquid and supercooled water, particularly concerning dielectric properties.
• This research offers a robust method for characterizing water's dynamic behavior and its response to thermal and density variations.