Casimir Forces Between Metal Surfaces

Such calculations were first carried out by their colleagues Casimir and Polder [17], who derived equations for the interaction of a single molecule with a perfectly conducting wall at distance D. Th obtained 

Casimir himself noted in his paper Although the effect is small, an experimental confirmation seems not unfeasible and might be of a certain interest.  

At this point we should darify that the Casimir force is not a really new type of force. It is simply another term for a special case of the van der Waals forces, namely, the retrarded van der Waals force between metallic surfaces. While the terms retarded van der Waals force or retarded London dispersion force are prevalent in the physical chemistry and colloid community, the term Casimir force or Casimir-Polder force has become popular in the physics community. This means that in principle the lifshitz theory is apphcable to describe the Casimir forces. The problem with using Lifshitz theory for ideal metals is the fact that for these the didectric constant diverges (e oo) and therefore the Lifshitz theory breaks down. However, for real metals, the use of the Lifshitz theory is possible with corresponding dielectric models of the metals. 

The simple form of Eq. (2.88) is appealing, especially when compared to the more complicated equations of the Lifshitz theory. However, one should not forget that the derivation of Eq. (2.88) was done under assumptions that are usually not fulfilled in practical situations  

We briefly discuss the relevance of the above assumptions for real experiments on 

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Recently, there have been measurements of retarded van der Waals forces between metal surfaces in liquid [145]. The forces were termed Casimir forces. 

Bressi, G., Carugno, G., Onofrio, R., Ruoso, G. Measurement of the Casimir force between parallel metallic surfaces. Phys. Rev. Lett. 88 Art. No. 041804 (2002). 

One year later Mohideen and coworkers [115] used the colloid probe AFM technique to probe the Casimir force between a metalcoated planar surface and a metal coated sphere. After several improvements [135], they could achieve a measurement over the range of distance starting from 62 to 400 nm with an experimental error ofless than 1% at the lowest distance (Figure 2.10). This level of precision allows a quantitative comparison with theory. In this case, the influences of surface roughness, finite temperature, and finite conductivity of the metal have been taken into account. 

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