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Materials

Van der Waals Force Measured Between Atoms

Laser technique confirms theoretical predictions

by Jyllian Kemsley
July 15, 2013 | A version of this story appeared in Volume 91, Issue 28

The van der Waals force is an attraction between neutral atoms, molecules, or other particles. Although it is weak, it plays an important role in phenomena such as adhesion of gecko toes and tape, condensation of nonpolar gases, and molecular self-assembly. The weakness, however, makes it difficult to study the force between individual particles. A research group led by Lucas Béguin of France’s National Center for Scientific Research has developed a way to measure the van der Waals interaction between two atoms (Phys. Rev. Lett. 2013, DOI: 10.1103/physrevlett.110.263201). The researchers trapped two rubidium-87 atoms in separate, tightly focused laser beams. Then they measured how the atoms oscillate between ground and highly excited states. The oscillation behavior depended on the distance between the atoms and the consequent strength of their van der Waals interaction. Béguin and his colleagues found that the van der Waals force they observed agrees with theoretical predictions for several excited states. The researchers are now exploring other aspects of van der Waals forces, such as the influence of geometry on interactions among multiple atoms.

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