Pure water is not just made up of H2O molecules

(ORDO NEWS) — Skoltech scientists, in collaboration with researchers from the University of Stuttgart, have shown that the concentration of short-lived ions (H3O + and OH-) in pure liquid water is much higher than that taken into account when assessing pH. This discovery significantly changes our ideas about the dynamic structure of water.

The ionic particles present in liquid water play an important role in redox processes, catalytic reactions, and electrochemical systems. It was previously assumed that nuclear quantum effects contribute to low-barrier tunneling of a hydrogen atom between water molecules, and the emergence of short-lived states with an excess proton. However, there was no experimental confirmation of this.

Skoltech scientists, in collaboration with German scientists, measured the ion-molecular composition of liquid water on a subpicosecond time scale. The result surprised scientists: they found that several percent of H2O molecules were temporarily in an ionized state.

Red, white, and black circles indicate the atoms of oxygen, hydrogen, and deuterium, respectively. Arrows indicate the directions of their oscillations.

“To determine the excess proton states, we used isotopologues of water: ordinary (H2O), heavy (D2O), and light heavy (HDO) water. Gradually replacing the hydrogen atoms (H) with deuterium (D), we changed the relative concentration of particles associated with the excess proton – HD2O +, DH2O +, H3O + and D3O +, and determined their contribution to the cumulative absorption in the infrared range. In the spectra of light heavy water near bending molecular modes, we found concentration-dependent spectral features that could not be described using any of the known models. We suggested that these features are associated with excess proton states that can occur on a picosecond scale, ”says one of the authors of the work, Skoltech Center for Energy Technology (CEST) Henny Werdan.

“Previous studies of the structure of water were based on crystallographic experiments and did not reflect the dynamics of water. Our work gives new insights into the complex structure of water on an ultrashort timeline. The results obtained suggest that in the future new effects of the interaction of the electric field and water, as well as other unusual properties of water will be detected, ”explained the first author of the article, CEST senior researcher Dr. Vasily Artyomov.


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