Self-energy, molecular size and shape

Other ions in the solution. The self-energy of a dipole embedded in a dielectric sphere is the key to Onsager s theory of the dielectric constant of dipolar fluids. Equally, in any theory for, say, the surface energy of water, or adsorption of molecule, the self-energy of a molecule as a function of its distance from an interface is involved. In adsorption proper, the same selfenergy for a molecule appears in the partition function of statistical mechaiucs from which the adsorption isotherm is derived. 

The idea is clear, but the details are complicated [3-12]. We omit details and focus on the results. 

In the non-retarded limit i.e. ignoring the finite velocity of light, the dispersion self-energy computed with this form factor can be shown to be [11, 12]  

The dispersion self-energy is of the same order of magnitude as the binding energy for a hydrogen atom, but of opposite sign. 

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