Abstract
We report on the anisotropic mass-dependent dispersion coefficients C-6(M=0,+/- 1) for He(1 S-1)-He(2 P-3) interaction using two different techniques. The first is a highly accurate Hylleraas basis-set diagonalization, while the second method is a semiempirical assessment based on tabulated oscillator strengths and available photoionization cross sections. The results from the two techniques agree to within 1.5%.