Supercooled water relaxation dynamics probed with heterodyne transient grating experiments

Year: 2006

Authors: Taschin A., Bartolini P., Eramo R., Torre R.

Autors Affiliation: European Laboratory for Non-Linear Spectroscopy (LENS), Università di Firenze, Via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy;
INFM-CRS-Soft Matter (CNR), c/o Università la Sapienza, Piazzale Aldo Moro 2, I-00185, Roma, Italy;
Dipartimento di Fisica, Università di Firenze, Via Sansone 1, I-50019 Sesto Fiorentino, Firenze, Italy

Abstract: We report results from a heterodyne-detected transient grating experiment on liquid and supercooled water in a wide temperature range, from -17.5 to 90 degrees C. The measured signal covers an extremely large time window with an excellent signal-to-noise ratio that enables the investigation in a single experiment of the sound speed and attenuation, thermal diffusivity, and temperature dependence of the dielectric constant. The experimental data clearly show the effect of the density and the temperature fluctuations on the water dielectric function. In order to describe the experimental results, we introduce a comprehensive hydrodynamic model taking into account the coupled density and temperature variables and their relevance in the definition of the spontaneous and forced dielectric variations. We use this model to describe the measured signal in transient grating experiments, including the heating and the electrostrictive sources produced by the laser excitation. The fitting procedure enables the safe extraction of several dynamic proprieties of liquid and supercooled water: the sound velocity and its damping, the thermal diffusivity, and the ratio between the dielectric thermodynamic derivatives. The measured parameters are compared to the literature data and discussed in the complex scenario of water physics.

Journal/Review: PHYSICAL REVIEW E

Volume: 74 (3)      Pages from: 031502-1  to: 031502-10

KeyWords: Electrostriction; Heterodyning; Permittivity; Signal to noise ratio; Supercooling; Thermal diffusion; Water, Dielectric variations; Laser excitation; Supercooled water; Thermodynamic derivatives, Dielectric relaxation
DOI: 10.1103/PhysRevE.74.031502

Citations: 32
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