Enormous Enhancement of van der Waals Forces between Small Silver Particles

Dispersion forces enhance the coagulation rate of small particles in a gas. Measurements of coagulation rates on ultrafine Ag and C particles with radii of 3-16 nm were performed. The results obtained with C particles almost agree with the expectations based on bulk electronic properties. However, Ag particles 14 nm in radius exhibit a very large coagulation rate. It points to an enhancement of the dispersion forces of at least a factor of ${10}^4$.