Long-range interactions of excited He atoms with ground-state noble-gas atoms

The dispersion coefficients $C_6$, $C_8$, and $C_{10}$ for long-range interactions of He($n{}^{1,3}S$) and He($n{}^{1,3}P$), $2\le n\le 10$, with the ground-state noble-gas atoms Ne, Ar, Kr, and Xe are calculated by summing over the reduced matrix elements of multipole transition operators. The large-$n$ expansions for the sums over the He oscillator strength divided by the corresponding transition energy are presented for these series. Using the expansions, the $C_6$ coefficients for the systems involving He($13{}^{1,3}S$) and He($13{}^{1,3}P$) are calculated and found to be in good agreement with directly calculated values.