Atomic Van der Waals force measured for the first time
Scientists in France are the first to make a direct measurement of the Van der Waals force between two atoms. They did this by trapping two Rydberg atoms with a laser and then measuring the force as a function of the distance separating them. The two atoms were in a coherent quantum state and the researchers believe that their system could be used to create quantum logic gates or to perform quantum simulations of condensed-matter systems.
The Van der Waals force between atoms, molecules and surfaces is a part of everyday life in many different ways. Spiders and geckos rely on it to walk up smooth walls, for example, and the force causes proteins inside our bodies to fold into complicated shapes.
Named after the Dutch scientist Johannes Diderik van der Waals – who first proposed it in 1873 to explain the behaviour of gases – it is a very weak force that only becomes relevant when atoms and molecules are very close together. Fluctuations in the electronic cloud of an atom mean that it will have an instantaneous dipole moment. This can induce a dipole moment in a nearby atom, the result being an attractive dipole–dipole interaction.