Electromagnetic-radiation absorption by water

P. Lunkenheimer, S. Emmert, R. Gulich, M. Köhler, M. Wolf, M. Schwab, and A. Loidl
Phys. Rev. E 96, 062607 – Published 11 December 2017

Abstract

Why does a microwave oven work? How does biological tissue absorb electromagnetic radiation? Astonishingly, we do not have a definite answer to these simple questions because the microscopic processes governing the absorption of electromagnetic waves by water are largely unclarified. This absorption can be quantified by dielectric loss spectra, which reveal a huge peak at a frequency of the exciting electric field of about 20 GHz and a gradual tailing off toward higher frequencies. The microscopic interpretation of such spectra is highly controversial and various superpositions of relaxation and resonance processes ascribed to single-molecule or molecule-cluster motions have been proposed for their analysis. By combining dielectric, microwave, THz, and far-infrared spectroscopy, here we provide nearly continuous temperature-dependent broadband spectra of water. Moreover, we find that corresponding spectra for aqueous solutions reveal the same features as pure water. However, in contrast to the latter, crystallization in these solutions can be avoided by supercooling. As different spectral contributions tend to disentangle at low temperatures, this enables us to deconvolute them when approaching the glass transition under cooling. We find that the overall spectral development, including the 20 GHz feature (employed for microwave heating), closely resembles the behavior known for common supercooled liquids. Thus water's absorption of electromagnetic waves at room temperature is not unusual but very similar to that of glass-forming liquids at elevated temperatures, deep in the low-viscosity liquid regime, and should be interpreted along similar lines.

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  • Received 13 March 2017
  • Revised 8 September 2017

DOI:https://doi.org/10.1103/PhysRevE.96.062607

©2017 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied PhysicsPolymers & Soft MatterPhysics of Living Systems

Authors & Affiliations

P. Lunkenheimer*, S. Emmert, R. Gulich, M. Köhler, M. Wolf, M. Schwab, and A. Loidl

  • Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany

  • *Corresponding author: peter.lunkenheimer@physik.uni-augsburg.de
  • Present address: Osram GmbH, 86153 Augsburg, Germany.
  • Present address: Instrument Systems GmbH, 81637 Munich, Germany.

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Issue

Vol. 96, Iss. 6 — December 2017

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