Retarded van der Waals Interactions. I. Simple Atoms

The effect of retardation on the dipole dispersion interaction between atoms has been determined. By the use of accurate frequency‐dependent polarizabilities, quantitative calculations of the retardation correction to the interaction of (H, H), (H, He⁺), (He⁺, He⁺), (H, He), and (He, He), as well as to the three‐body system (He, He, He), have been made. The procedure used was to evaluate the Casimir–Polder integral for two atoms and its three‐body extension directly so as to obtain results correct for all $R$ . Although the corrections to the limiting behavior (${\text{1\hspace{0.17em}/\hspace{0.17em}R}}^6$ for “small” ${\text{R, 1\hspace{0.17em}/\hspace{0.17em}R}}^7$ for large $R$ ) are not large, they may be of significance for high accuracy measurements in some cases.