Universal spherical nonsingular van der Waals interactions are developed through considering the effects of finite molecular size. The frequency integration upper limit of this interaction has been determined for the first time to be on the order of 1$0^{18}$ rad ${\mathrm{s}}^{-1\mathrm{}}$ regardless of the intermolecular separation. This potential has been tested successfully for the following representative systems: ${\mathrm{H}}_2$ $\left({}_{}{}^3{}_{}{}^{}\Sigma \right)$, H${\mathrm{e}}_2$, NaK $\left({}_{}{}^3{}_{}{}^{}\Sigma \right)$, and LiHg.

• Received 17 October 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.1724