The discovery of water molecules will force us to change textbooks

Textbooks will have to be changed after the new discovery that water molecules on the surface of salt water They are organized differently than expected in theory.

Many important reactions associated with climate and environmental processes occur when water molecules interact with air. For example, the evaporation of ocean water plays an important role in atmospheric chemistry and climatology. Understanding these responses is critical to efforts to mitigate human impacts on our planet.

The distribution of ions at the air-water interface can influence atmospheric processes. However, the precise understanding of the microscopic reactions at these important interfaces is still under active debate.

In an article now published in the magazine Natural chemistryResearchers from the University of Cambridge and the Max Planck Institute for Polymer Research in Germany show that the ions and water molecules on the surface of most salt water solutions, known as electrolyte solutions, They are organized completely differently than traditionally understood. This could lead to improved atmospheric chemistry models and other applications.

The researchers set out to study how water molecules are affected by the distribution of ions at the exact point where air and water meet. Traditionally this was done using a technique called Total oscillation frequency generation (VSFG).

Using this laser beam technique, molecular vibrations can be measured directly at these key interfaces. However, although signal intensity can be measured, This method cannot determine whether signals are positive or negative, which has made results difficult to interpret in the past.. In addition, exclusive use of experimental data may produce mixed results.

The team overcame these problems by using a more complex form of VSFG, called heterodyne sensing (HD) VSFG, to study different electrolyte solutions. They then developed advanced computer models to simulate interfaces in different scenarios.

The combined results showed that both positively charged ions, called cations, and negatively charged ions, called anions, are depleted at the water/air interface. The cations and anions of simple electrolytes orient water molecules both up and down. This is a change in textbook models, which teach that ions form an electrical double layer and orient water molecules in one direction.

Co-senior author Dr Yair Litman from the Yusuf Hamid Department of Chemistry said: “Our work shows that the surface of simple electrolyte solutions has a different ion distribution than previously thought and that the ion-rich subsurface determines how the interface is organized: on top there are several layers of pure water, then an ion-rich layer, and finally a bulk brine solution.”