As onw of the weakest chemical interactions, van der Waals forces are difficult to study. With the development of nanotechnology, which opperates at the scale where the effect of the forces are felt, the need to understand these forces is becoming more important.

To study the van der Waals force, Alex Cronin and co-workers, University of Arizona, USA, have measured the interactions between single atoms and a surface. Using a nanograting, the team measured the diffraction of atoms. Different atoms (Li, Na, K, Rb) were used to obtain a ratio of van der Waals coefficients for the same surface.

The van der Waals coefficients were seen to be strongly influenced by the core electrons, with only a weak influence being present from permittivity and geometry of the surface. These measurements reduce the uncertainty in the coefficient ratio to 2 %.

• Atom Diffraction Reveals the Impact of Atomic Core Electrons on Atom-Surface Potentials
  V. P. A. Lonij, C. E. Klauss, W. F. Holmgren, A. D. Cronin,
  Phys. Rev. Lett. 2010, 105, 233202
  DOI: 10.1103/PhysRevLett.105.233202