Amazing stuff! Water is still a mysterious substance!
"A hydrogen bond is an electrostatic attraction between molecules, mediated by a positively charged hydrogen atom. This relatively weak bond—first theoretically described in 1920 —is the fundamental binding force in water, explaining many of this liquid’s unique properties, such as its high surface tension and unique attributes as a solvent.
Within the hydrogen-bonded network connecting H2O molecules in water and ice, stronger hydrogen bonds can form short-lived chains, called water wires, but the effect of these linear structures is still debated.
Molecular simulations suggest that water wires provide important pathways for proton transfer, but direct observational evidence has been lacking.
[Researchers] propose a way to measure the presence of water wires ... Through rigorous electronic-structure calculations and molecular-dynamics simulations, the researchers show that elusive water wires can be detected in bulk water and ice by measuring light absorption in the UV-to-visible range. The technique could be used to study how water-wire behavior changes under different spatial and thermal conditions. ..."
From the abstract:
"Water wires, quasi-one-dimensional chains composed of hydrogen-bonded (H-bonded) water molecules, play a fundamental role in numerous chemical, physical, and physiological processes. Yet direct experimental detection of water wires has been elusive so far. Based on advanced ab initio many-body theory that includes electron-hole interactions, we report that optical absorption spectroscopy can serve as a sensitive probe of water wires and their ordering.
In both liquid and solid water, the main peak of the spectrum is discovered to be a charge-transfer exciton.
In water, the charge-transfer exciton is strongly coupled to the H-bonding environment where the exciton is excited between H-bonded water molecules with a large spectral intensity.
In regular ice, the spectral weight of the charge-transfer exciton is enhanced by a collective excitation occurring on proton-ordered water wires, whose spectral intensity scales with the ordering length of water wire. The spectral intensity and excitonic interaction strength reaches its maximum in ice XI, where the long-range ordering length yields the most pronounced spectral signal.
Our findings suggest that water wires, which widely exist in important physiological and biological systems and other phases of ice, can be directly probed by this approach."
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