Knowledge Bank

The oscillator strength sums {S}(-{k})=-\frac{2}{3}(2{j}+1)^{-1}\sum_{{J}^{\prime}}<{J}\parallel{R}^{(1)}\parallel{J}^{\prime}><{J}^{\prime}\parallel{R}^{(1)}\parallel{J}>(-)^{j^{\prime}-j}/({E}{j}-{E}{j})^{{k}-1} for k=1,2,3 have been calculated for the atoms He thru Kr. The sum S ($-1$) is calculated directly from analytical Hartree-Fock wavefunctions and S ($-2$) and S ($-3$) are found via a variational method $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}$ The interpolated values of S ($-1.5$) gave the spherically averaged dispersion coefficient as $C6=34S(-1.5)2$ for the homonuclear $diatomics.2$