Abstract

An attempt is made to systematize the general calculation of the interaction energy of a pair of atoms each of which has one or two equivalent $s$-electrons outside of closed shells. General expressions for this energy are set up in terms of certain integrals and these integrals are evaluated for wave functions of Slater's type in terms of functions which are either tabulated or derivable from those in the accompanying tables. The method is applied to the calculation of some of the constants of a normal ${\mathrm{Na}}_{2}$ molecule (which show fair agreement with the experimental values) and the repulsion energy of two normal helium atoms.